Book of Nature, Origin and Development of the Metaphor

I. Introduction

The contemporary dialogue between science and theology is often presented in terms of a comparison between the “Book of Nature” and the “Book of Scripture.” There are basically two ways in which this metaphor can be used. In the more general way, the metaphor of the Two Books refers to the comparison between the knowledge of nature achieved by science and the one achieved from the Judaeo-Christian Revelation, that reads and understands nature as creation. In this case it is nothing but a different way of referring to “Science and Religion” as a topic under debate. However, we can refer to the term “book” also in a specific and definite manner. In this case the metaphor of the Book of Nature is used to emphasize the parallel between nature and a “written document.” That is, a document written by someone and addressed to someone else; a document intended to convey an intelligible content; a text that might require a certain effort to be properly interpreted and explained according to its author’s original meaning. However, if everyone understands what we mean when speaking of Scripture as a book, it might be less clear what we mean when speaking of the cosmos “as a book.” Is this analogy truly meaningful? Metaphor is a form of analogy, of course, but quite weak, and admits degrees and nuances. The main question is then: are we allowed to consider nature as a book and, more definitely, how was such a metaphor employed throughout the history?

When speaking of the relationship between the Two Books, one first thinks to what happened from the XVII century onward, that is, from the epoch in which the so-called scientific revolution began to put in question some relevant belief owned by the theological establishment. It was in that context when we began to speak of a “conflict” between the Two Books. Prior to that epoch the use of the metaphor could seem less significant, and the whole subject lacking in interest. In reality, the image of nature as a “book” had a wide literary usage well before the epoch of Galileo and Kepler. It is worthwhile, then, to investigate what happened also before the scientific revolution, in order to shed light on how the main philosophical ideas concerning the Two Books (readability, harmony, conflict, mutual interconnection, etc.) evolve through history. The history of the concept of nature should be taken also in account, as well as the epistemological consequences entailed by accepting that nature is truly a book. It is easy to see that the whole history of philosophy and the whole history of science seem to be here involved, including their relationship with theology (essential outlines in Lindberg and Numbers, 1986; Brooke, 1991; Clarke, 1993; and, especially, Crombie, 1994). For all these reasons, an exhaustive answer to the previous questions is beyond the aims of this paper. Therefore, I will confine myself to recall the heritage and the most important historical hallmarks of the metaphor, pointing out the major philosophical and theological implications here entangled, especialy those concerned by Fundamental theology.

II. The theological import of the metaphor of the Book

1. Scholarly contributions and their different perspectives: a short status quaestionis. Recent times have witnessed a remarkable interest of theology in the metaphor of the Book of Nature, to express the created world as a locus of divine presence and revelation. In recent Magisterium of the Catholic Church, the metaphor has been mentioned by John Paul II in Fides et ratio (n. 19), Benedict XVI in Verbum Domini (nn. 6-21) as well as in other documents (cf. for example Caritas in veritate, n. 51), and Francis in Laudato si’ (nn. 12, 85, 239). Indeed, interest in the metaphor reaches far beyond the theological domain: for many centuries it has attracted continuing fascination in a range of contexts including literature, art and particularly the natural sciences. However, the image of the Book of Nature does not seem to have obtained, in recent times, a specific theological development. Actually, XX century Fundamental theology paid less attention the notion of revelation of God through the created world, compared with the wide room given to God’s revelation through the history of salvation, centered on the religious experience of the people of Israel (see Sánchez-Cañizares and Tanzella-Nitti, 2006). Furthermore, the metaphor is far from having an established meaning; it has been employed within a wide range of cultural, philosophical and theological contexts for very different purposes. In Patristic and Mediaeval literature, nature as a book was seen in harmony with the Sacred Scriptures, whereas from the early Modern era onwards it was presented also as an autonomous book, other than biblical Revelation. Looking at the present time, a risk of misunderstanding arises, because many webpages, institutes and programs of spirituality propose to re-evaluate, or be in tune with, the “Book of nature.” This gives rise, for instance, to the circulation of dubious quotations, as well as the tendency to mix Christian and non-Christian sources, as if they were necessarily speaking about the same thing. For all these reasons, the use of the metaphor of nature as a book remains a delicate question.

In general terms, linguistic and literary studies seem to have dominated this research field. The classic reference is that to Curtius’ European Literature and the Latin Middle Ages (1948), which includes a chapter on the metaphoric uses of the book in the history of literature and quotes various (mainly Mediaeval) instances of nature as a book. The metaphorical approach is applied more systematically in Rothacker’s Das Buch der Natur (1979) which, however, is only a collection of citations, the majority of which are from the age of Romanticism. A third major contribution is Blumenberg’s Die Lesbarkeit der Welt (1981), which uses both of the previous studies as well as other sources to provide a more systematic analysis of the history of the idea that the world is readable. Yet Blumenberg’s methodology is decidedly “metaphorological” (the term is his), and little attention is paid to the theological dimension of the question.

More recently, there have been a range of new studies, particularly the two series of volumes edited, respectively, by Vanderjagt and van Berkel (2005-2006), and by van der Meer and Mandelbrote (2008), that include historical surveys and analyses of the metaphor. There are important contributions in these volumes, although their focus is overwhelmingly on Mediaeval and Modern sources, paying less attention to the Classical and Patristic Ages, when the metaphor was born. I proposed a more theological approach in my article The Two Books prior to the Scientific Revolution (2004) and, more recently, in a section of vol. 3 of my Treatise on Fundamental Theology in Scientific Context (2018), which includes a chapter dedicated to the revelation of God through creation. As far as I know, there are no monographic studies that would set a clear framework and analyze the historical uses of the metaphor across different authors. Useful ideas, however, are contained in a number of studies of theological character (see, for instance, Blowers, 2008 and 2012; Lollar, 2013). A PhD thesis by the Finnish scholar Oskari Juurikkala, entitled The Patristic and Mediaeval metaphor of the Book of nature: implications for Fundamental theology (2019) is in press.

2. Historical steps and some hermeneutical clarifications. Authors are still far from reaching a common view on many aspects of the metaphor. For instance, regarding its very historical origin, Curtius and Blumenberg provide some indications that the underlying idea would be found in ancient Mesopotamia and possibly (with doubts) in ancient Greece; however, almost the entire patristic literature is ignored, with the exception of some references to St. Augustine (354-430) (cf. Curtius, 1948, pp. 302-311; Blumenberg, 1981, chpts. 3-4). Drecoll (2005) has argued that the specific expression liber naturae (that is, the typical mediaeval and modern expression) is not found before Augustine, but he studies only a specific combination of words, whereas the concept of book is certainly applied metaphorically to created nature before Augustine, at least by Anthony, Ephrem the Syrian (c. 306-373) and Evagrius Ponticus (c. 345-399). Blowers has quite convincingly argued that the beginnings of the analogy between Scripture and cosmos as ‘Two Books’ should be traced back to Origen (184/185-253/254) (cf. Blowers, 2012, pp. 318-319; cf. also Benjamins, 2005). All of these arguments may even be valid in terms of the parameters set by each of the studies; but then, their variety reveals the need for a detailed and systematic analysis of the origins and gradual development of the metaphor.

Unfortunately, the literature about the theoretical foundations, in the Patristic period, of the image of nature as a book is very limited. Blowers has highlighted the centrality of the Greek notion of logos, but he didn’t elaborate much on the argument, and his research is principally concerned with the spiritual dimension of theology of creation, where the metaphor can appear a peripheral matter (cf. Blowers, 2012, pp. 318-322). Biblical theology is surprisingly silent on the subject, although it should be clear that the origin of all the things from the Word of God, has much to do with the idea that the various creatures can speak of their Creator, like the words of a book speak of their Author.

As far as the Mediaeval period is concerned, the way in which the metaphor is transmitted and received by the previous Patristic period raises some questions. In the secondary literature, the Mediaeval Book of Nature is routinely associated with Augustine (cf. Blumenberg, 1981, ch. 5; Nobis, 1971, pp. 957-959). However, it is quite probable that while this concept referred to Augustine for being the greatest of all the patristic authorities for the Latin Middle Ages, actually the underlying theological insights came from somewhere else. It seems that a key-role was played by John Scottus Eriugena (c. 810-877), who transmitted to the Latin environment the ideas of the Greek Fathers: the Cappadocians, Pseudo-Dionysius, and most importantly Maximus the Confessor. Concerning the subsequent development of the Mediaeval metaphor, pride of place has conventionally been given to Bonaventure (1221-1274), although he was essentially using ideas common in the XII century, especially those contained in the writings of Hugh of Saint Victor (1096-1141).

Regarding the theological foundations and implications of the Mediaeval metaphor, the issue may be addressed of what are the continuities and discontinuities with respect to the Patristic texts. Of course, there are significant continuities, which suggest that there is already a well-established tradition, only undergoing small changes of emphasis and perspective. On the other part, the Middle Ages bring about at least three important novelties. First, we perceive a growing skepticism with respect to the intrinsic value and readability of nature due to the weight of sin; the issue it not entirely new, yet Augustine himself spoke of that, but it acquires now more explicit expression, enriching the metaphor with a third book, the Book of the Cross. Second, while the Patristic metaphor was predominantly conceptualized in terms of the spoken word (based on the divine Logos and the logoi that the creature are), the Mediaeval Book of Nature (and the various sub-metaphors to which it gives rise) is increasingly presented as something which must be seen, not only heard, according to the attention this period paid to images and symbolic language. Third, in each period the metaphor reflects the framework offered by the theology of the period: God’s call to salvation, the relationship between creation and redemption, the role of the Incarnated Word, all subjects about which the Fathers of the Church and the Middle Age authors didn’t have the same and identical perspective. It is known, for instance, that in the Middle Age the theological emphasis was mainly on redemption and Christology, while the language turned more symbolic and rational compared with that employed by the Fathers.

Leaving aside the understanding of the metaphor during the revival of naturalistic studies experienced by the Renaissance, the more intriguing period for studying contents and implications of the Book on Nature remains the Modern Age. First of all, it must be stressed that many of the consequences which will come into light later, in the XVII and XVIII centuries, were surprisingly prepared by the Liber creaturarum by Raymond of Sebond (1385-1436), a text that the Italian scholar Lino Conti has the merit to have underlined and commented in recent years (see Conti, 2004). The autonomy of nature, that of its own language, and the possibility of a closer vis-à-vis confrontation with the Book of Scripture, are all seeds present in Sebond’s view that, probably beyond his own expectations, brought about much stronger effects during the scientific revolution. Secondly, the Modern Age is witness of very different views about the readability of the Book of Nature. A Neo-platonic perspective, inherited by the Academies of the Renaissance, which confines the usability of the Book to those who know the language of mathematics and geometry, is opposed to the perspective that considers Nature as a public book, readable by everyone. However, as we will see in a next section, in this last view co-exist two different attitudes: one that states that the Author of Nature’s Book is the same Author of sacred Scriptures, the other quite critical with respect to a specific divine Revelation in history. In the Modern Age the Book of Nature could be used either to give rise to a religion of nature or to reinforce the religion of the Judaeo-Christian tradition. Among the scholars who faced this quite intriguing period it must be quoted Peter Harrison (see Harrison, 1998, 2006 and 2007), but a systematic and exhaustive study is, at the moment, still lacking.

3. The role of the metaphor in the frame of Fundamental theology. The interest of Fundamental theology is not, primarily, to focus on the metaphor as a linguistic phenomenon, but to highlight the theological idea that the metaphor seeks to express. Moreover, if theology studies why and how nature was seen as a book, it is not for the sake of historical curiosity, but as a way of illuminating present-day questions and discussions around the relation between faith and reason. Consider the following topics: a) the salvific value of the contemplation of nature; b) the revelation of God through creation; c) the interrelation between creation and redemption; d) biblical exegesis and the natural sciences; e) the inter-religious dialogue starting from nature, etc.

The main philological, linguistic and historical questions, propaedeutic to the theological ones, mainly regard the period from the Antiquity to the early Modern Age and could be summarized as follows: a) the key Patristic and Mediaeval texts in which the metaphor is found; b) their status in terms of textual critique (authenticity, expressions truly used, etc.); c) their true hermeneutical context (type of literature, the context in which the idea appears, motivation); and d) what tradition the texts inherited, that is, what are their assumptions and antecedents. These questions seek to identify more precisely the relevant texts so as to enable us to analyze the historical origination, diffusion and evolution of the metaphor.

On the other hand, there are more properly theological questions, which go beyond the texts and the words used and, in a sense, go even beyond the metaphor itself, because they “open” the notion of book toward other relevant notions as logos, words, letters, voices, mirror, etc. Taking into account the broader perspective of theology, the first point to clarify is what is the underlying theological foundation and vision that give rise to the metaphor (for example, the presence of the Logos in creation, allegorical exegesis, sacramental theology based on symbolic language, etc.). Only after this previous analysis, theology can address its more relevant questions and implications as, for instance, if the Book of Nature has any moral and/or salvific relevance for those who read it, or what does the Book of Nature reveal about God, his attributes, his will and his salvific plans for all mankind. In answering these questions, theology is highly interested in investigating the Christological dimension of the “book.” In other words, what the metaphor means and the extent to which it can be used, is expected to depend, in its deeper and ultimate level, on the Christological understanding of creation, of the Scriptures and of the human beings.

There is a number of elements in Patristic theology that seem to provide a solid theological basis for the grounding and further development of the metaphor. The most important of these was the correspondence between the cosmological logos of Greek philosophy and the biblical idea of the divine word of creation. Other ideas, such as the existence of a natural law (understood both cosmically and morally), the contemplation and beauty of nature as a work of God, and the practice of allegorical interpretation of Scriptures, may also have contributed to the success of the metaphor. Although we cannot definitively determine the role and influence of each author, nevertheless we can state without doubt that the theology of the divine Word, that is the role of Logos in the work of creation, is central to the Patristic and Mediaeval idea of nature as a ‘book’; it is repeatedly found in the context of theology of creation, and over time it becomes more and more clearly expressed in the idea of the logoi that creatures are. In contrast, the significance of the other elements is more varied. For instance, the natural law is particularly important to Maximus, and it plays a role in Ephrem; but it is quite marginal in Bonaventure, probably because his extensive doctrine of the natural law was mainly confined to its interior dimension. The notion of the contemplation of nature, on the other hand, is found in numerous texts, and it is important to most of the thinkers. Allegory is present in some cases, but many times the metaphor is not based on any allegory at all; rather, it is derived from a parallelism between Scriptures and creation, which is much more than an allegory, because Scriptures and creation have the same origin and finality in the divine Logos. Even the authors of the Middle Age, who bent toward a symbolic language, as Scottus Eriugena, Hugh of St. Victor and Bonaventure, do not derive the metaphor from symbolic considerations only.

If we consider pre-Christian texts, they provide of course some preparation to the Christian metaphor of the Book of Nature, but confine themselves to heavenly characters. The religiosity of many ancient cultures spontaneously attributed a certain sacrality to the heavens, which were understood as the place for a dialogue between the god(s) and the human beings. However, it was the Christian doctrine of the Incarnated Logos that enabled the understanding that the presence of and communication with the divine may be sought and found in all created realities, without any loss of divine transcendence. The Christian understanding (and transformation) of the cosmological logos of Greek philosophers was fundamental for this new vision, because it provided the conceptual tools for distinguishing between the transcendent (non-immanent) Logos and the created logoi, the latter of which are not identified with the Logos, but are inseparable from him, and therefore intrinsically related to all the creative, revelatory and redemptive activity of the divine Logos, Jesus Christ.

4. The contemporary revival of the Book of Nature in the teachings of the Catholic Church. Concerning the implications of the metaphor for today’s theology it should be noted that some of them are intrinsic to the view of nature as ‘a book,’ while others refer to the idea of having two books, namely Nature and Scripture, authored by the same God. In the first case, considering nature as a book is a fruitful image, because it easily associates to the created world all the characters of a true divine revelation. In fact, a book manifests the person/personality of its Author; it transmits a Word and expresses an intentionality; it contains an intelligible message; it is communicable and universal even though it requires a certain work of interpretation; it is able to rise the interest of the addressee and demands for his answer; its origin is a person and it is directed to a personal interlocutor. All these characteristics are important to understand the cosmos as the place of a true divine revelation, and would suffice to justify the interest of theology toward those approaches and authors, in the past as well in the present times, who have employed or still use the metaphor.

The pontifical Magisterium of recent decades seems to have seized this opportunity, at least judging by the high number of references to the Book of Nature in documents of certain relevance. In a page of Fides et ratio (1998), John Paul II defines this book as “the first stage of divine Revelation […] which, when read with the proper tools of human reason, can lead to knowledge of the Creator” (n. 19); an idea he resumed and developed during a couple of Wednesday catechesis, given on occasion of General Audiences (cf. John Paul II, General Audiences, August 2, 2000; January 30, 2002). Benedict XVI quotes the metaphor in the encyclical Caritas in veritate (2009; cf. n. 51), and speaks of it widely in the post-synodal exhortation Verbum Domini (2010). In this last document, he states that “while the Christ event is at the heart of divine revelation, we also need to realize that creation itself, the liber naturae, is an essential part of this symphony of many voices in which the one word is spoken” (n. 7); then, he adds, “we can compare the cosmos to a ‘book’ […], the work of an author who expresses himself through the ‘symphony’ of creation” (n. 13). There are about a dozen speeches by this Pontiff —addresses, catechesis and speeches of various kinds— which speak of nature as a book that the Creator offered to us. Benedict XVI often uses this image to point out that the rationality of creation and the rationality of the human mind, capable of understanding it, both have their origin in God (See Benedict XVI, Discourse to the Roman Curia, December 22, 2005; Discourse to the Pontifical Academy of Sciences, October 31, 2008; Homily on the Solemnity of the Epiphany, Rome, January 6, 2009; Message to the participants to the Conference “From Galileo’s telescope to evolutionary cosmology”, Rome, November 26, 2009; Message for the World day of Peace: “If you want to cultivate peace, protect creation,” December 8, 2009; General Audience, March 24, 2010; Discourse to the General Assembly of the Italian Bishop Conference, May 27, 2010; Homily in the Church of the “Sagrada Familia,” Barcelona, November 7, 2010; General Audience, February 6, 2013). The metaphor is well present also in pope Francis Encyclical Laudato si’ (2015): “God has written a precious book —the Pontiff says— whose letters are the multitude of created things present in the universe.” (n. 85; see also nn. 6, 11, 12, 239). The metaphor was proposed also in other occasions (cf. Homily on the Solemnity of Epiphany, Rome, January 6, 2014).

It is to note that the author most frequently mentioned by the Magisterium of the popes is, in this context, Galileo Galilei, who also uses the metaphor, as we shall see later, in various places in his works (cf., for instance, John Paul II, Fides et ratio, n. 34, footnote 29; Benedict XVI, Discourse to National Assembly of the Italian Church, Verona, October 18, 2006; Discourse to the Pontifical Academy of Sciences, Rome, October 31, 2008; Message to the participants to the Conference “From Galileo’s telescope to evolutionary cosmology”, Rome, November 26, 2009; Verbum Domini, n. 30). Is there any particular reason to refer to Galileo, given the wide choice of possible authors, including many Fathers of the Church, many Mediaeval theologians and not a few Modern authors? The question is not irrelevant, bearing in mind the long history of the metaphor and the specific use that Galileo makes of it, according to the Neo-platonic view of the Renaissance Academies. This choice could be the result of a kind of “overexposure” of the Galileo affair, so that the Catholic Church likes to mention Galileo when she deals with issues related to the natural sciences. Galileo’s sentences are well known and, perhaps, also more available than quotations coming from other sources, even if more pertinent. Moreover, Galileo is an emblematic figure: when the Magisterium quotes his passages about God as the author of the book of the world, it wants to endorse the harmony between science and faith by employing the same words of the Italian scientist. However, when it is done without offering further details, the complex history of the metaphor runs the risk of being bracketed out. In so doing, the differences between the way in which Galileo makes use of the metaphor and the use made by other authors before him, the Fathers of the Church in particular, run the risk of being underestimated.

In the second case, when the metaphor refers to the “Two Books,” Nature and Scripture, theology is easily induced to employ it just to frame the relationship between faith and reason, or that between faith and science, within a captivating image, clear to a wide public. Here too, Galileo remains the most cited source. However, if we look at the issue closely, there is something to be made precise. If the image of the “Two Books” is used to express the two modalities of the same divine Revelation, namely revelation through creation and revelation through the biblical message, we must remember that in Catholic theology, different from the perspective endorsed by the majority of authors belonging to the Protestant Reformation, the book of Scripture does not express, alone, the entire historical-supernatural Revelation, which includes, for Catholics, also the role of Tradition.

III. The development of the metaphor within the Christian tradition

1. Does the Bible see the cosmos as a book?. It is well known that the Sacred Scriptures introduce the created world as an effect of the Word of God: “Then God said, ‘Let there be light’, and there was light...” (Gn 1:3). This relationship between the world and the Word is strengthened in the New Testament, which affirms the dependence of the entire universe on the Word made flesh: “in these last days, he spoke to us through a son, whom he made heir of all things and through whom he created the universe [...] and who sustains all things by his mighty word” (Heb 1:2-3). Creatures themselves are voices, which praise the Lord (cf. Dn 3:57ff; Ps 150:6). Made by the Logos, all creatures are logoi, which express themselves as voices or words. Looking at creatures as the letters of a book, or as the voices of a choir, is nothing but a consequence of a theology of creation centered on the Word-Logos. By words we narrate a text, we pray hymns or sing a song. A theology of Logos, then, is much more appropriate to show a relation between nature and God that considers creatures like “words,” compared with other kinds of relations that look at creatures like the footprint, the traces or the mirror of God the Creator. The metaphor of nature as a book finds its roots in this view of creation. However, it does not mean that the image of the book, as such, is present throughout the Bible.

Nevertheless we have a number of pages which describe the appearance of the cosmos, especially the appearance of the sky, using the metaphor of a tent or a curtain. The heavens are spread out, or even stretched out, like a tent over the Earth, as we read in many passages from the Psalms, the books of Isaiah or Job: “He commands the sun, and it rises not; he seals up the stars. He alone stretches out the heavens and treads upon the crests of the sea. He made the Bear and Orion, the Pleiades and the constellations of the south.” (Jb 9:7-9. Cf. Ps 104:1-4; Is 45:12; Jer 10:12=51:15). The verbs here used correspond to the action of pitching and fixing a tent, or rarely, to the action of extending a cloth. In the apocalyptic context of God’s final judgement, we read in the Book of Isaiah: “The heavens shall be rolled up like a scroll, and all their host shall wither away. As the leaf wilts on the vine, or as the fig withers on the tree.” (Is 34:4). A parallel page is presented by the Book of Revelation: “Then the sky was divided like a torn scroll curling up, and every mountain and island was moved from its place.” (Rv 6:14). All these passages seem to indicate that, within the metaphor of the stretched curtain, the curtain is like a scroll; the action opposite to that of laying out (or also of creating) the heavens is that of curling or rolling them back, similar to a scroll. They are stretched out when God make all things, and will be rolled up in future times, in a new creation. The point to be mentioned is that ‘scroll’ is also the term used by the Bible to indicate a book, thus suggesting that the heavens may be seen as both a curtain and a scroll.

From a merely philological point of view, we do not have enough data to conclude that the Bible uses the explicit metaphor of the Book of Nature, but some passages are certainly inspiring in this respect. The root of the metaphor, as we said before, must be seen, rather, in a view of creation centered on the theology of the Word-Logos, which gives to the cosmos rationality and intelligibility, making the world readable. The association between “nature as creation”, and “nature as a book”, relies upon the clear association existing between the world and the Word, a relationship that is remarkably theological in character. God creates by his Uncreated Word and the world conveys a divine logos, i.e. contains and expresses the logoi of God.

2. The Fathers of the Church and the early Christian writers. The view that the existence of a Creator can be deduced starting from the observation of His works, and the belief that through these works He speaks to us, are ideas which belong from the very beginning to the history of human culture. Although we cannot exclude that the attitude of looking at Nature as if it were a book was present in ancient cultures – for writing techniques were spread throughout the Mediterranean area from 3500 B.C. – this view first began to be clearly recorded in early Christian literature. The Fathers of the Church employ it in two main ambits, namely the so-called cosmological argument, by which they invited the acknowledgment of a provident God-Creator starting from the observation of the order and beauty of creatures, and the cosmic dimension of liturgy, for God had to be celebrated and praised in His glory also in the context of Nature. By the same words of Anthony the Abbot (3rd Century), probably the first example of hermitage, “my book is created nature, which is always at my disposal whenever I want to read God’s words.” (cf. Socrates Scholasticus, Historia Ecclesiastica, IV, 23; PG 67, 518). As pointed out a bit later by Isaac of Nineveh, Nature was given to human beings prior to them receiving the sacred Scriptures (cf. Sermones ascetici, V). Among the Fathers of the Church, explicit references to the Book of Nature can be found, among others, in Basil of Cesarea, Gregory of Nyssa, John Chrysostom, Augustine of Hyppo, John Cassian, Ephrem the Syrian, Maximus the Confessor. If we also include those authors who implicitly refer to the Book of Nature, for example those who convey the idea that God speaks to us through creation, the list would become much larger. It is enough, for our purposes, to offer here some quotes.

According to the Greek father Basil of Cesarea (329-379) “We were made in the image and likeness of our Creator, endowed with intellect and reason, so that our nature was complete and we could know God. In this way, continuously contemplating the beauty of creatures, through them as if they were letters and words, we could read God’s wisdom and providence over all things.” (Homilia de gratiarum actione, 2: PG 31, 221C - 224A). Among the Latin Fathers it is Augustine of Hyppo (354-430) who dedicates various passages to the Book of Nature, including interesting comparisons with the book of Scriptures. “It is the divine page that you must listen to; it is the book of the universe that you must observe. The pages of Scripture can only be read by those who know how to read and write, while everyone, even the illiterate, can read the book of the universe.” (Enarrationes in Psalmos 45, 7: PL 36, 518). “Some people — we read in one of his Sermons — in order to discover God, read a book. But there is a great book: the very appearance of created things. Look above and below, note, read. God whom you want to discover, did not make the letters with ink; he put in front of your eyes the very things that he made. Can you ask for a louder voice than that?” (Sermones, 68, 6: PLS 2, 505). In a page of his Confessions, Ch. XIII, the metaphor of heaven as a book is combined with the biblical image of the starry sky stretched over us like a skin. God clothed our naked first parents with a skin just after they sinned, thus showing His mercy for us; likewise the heavens are a skin which also shows God’s mercy, because, reading them as in a book, human beings can know the will of God and behave in a virtuous and honest way (cf. Confessiones, XIII, 15, 16). Referring to creation, Augustine says: “For we know no other books which so destroy pride, which so destroy the enemy, who resists your reconciliation by defending his own sins.” (Confessiones, XIII, 15, 17). In contrast to human beings, the angels do not need to read the heavens, for they always behold God’s face and perfectly know God’s will: indeed, God himself is their book (cf. Confessiones, XIII, 15, 18).

On our topic, a remarkable influence was exerted by Maximus the Confessor (580-662) over the centuries that followed, especially during the Middle Ages. Commenting on the event of Christ’s Transfiguration, he compares Nature and Scripture to two garments with which the Incarnated Logos was endowed; the natural law being his humanity, and the divine law, revealed by Scripture, his divinity. These two laws were presented to us by means of two different books, Nature and Scripture. They both veil and reveal the same Logos, they have the same dignity and teach the same things. Maximus is even more explicit: the two books have more or less the same content and he who want to know and carry out God’s will, needs them both (cf. Ambigua, 10: PG 91, 1128 C).

In reading the Book of Nature, the deep mystery of the Logos does not vanish, nor is it destroyed. “The natural law, as if it were a book, holds and sustains the harmony of the whole of the universe. Material bodies are like the book’s characters and syllables; they are like the first basic elements nearer to us, but allow only a partial knowledge. Yet such a book has also more general and universal words, more distant from us, whose knowledge is more subtle and difficult to reach. The same divine Logos who wrote these words with wisdom, is likewise embodied in them in an ineffable and inexpressible way. He reveals himself completely through these words; but after their careful reading, we can only reach the knowledge that he is, because he is none of those particular things. It is gathering with reverence all these different manifestations of his, so that we are led toward a unique and coherent representation of the truth, and he makes himself known to us as Creator, by analogy from the visible, created world.” (Ambigua, 10: PG 91, 1129 A). It is worthwhile to mention here the great equilibrium showed by Maximus Confessor. On one hand he affirms the need to know the natural law, and maintains that all that is contained in the Holy Scriptures is also contained in Nature (a statement which some centuries later would have brought about some critical consequences). On the other hand, faithful to the Greek tradition, he is aware that the knowledge of God through the Book of Nature remains veiled, deficient, and certainly inferior to that provided by the Bible.

John Scottus Eriugena (about 810-877) observed that at the very beginning of the history of salvation Abraham was invited to recognize God not looking at the Scriptures, that did not exist yet, but by looking up at the starry sky (cf.  De divisione naturae: PL 122, 723-724). In the works of the Celtic theologian, the idea that God reveals himself through the two Books is also present. Nature and Scripture can be both considered as God’s theophanies. “The eternal light manifests it to the world in two ways, through Scripture and through creatures. In no other way the knowledge of God is renewed in us but in the characters (Lat. apices) of Scripture and in the forms (Lat. species) of creatures.” (Homilia in prologum S. Evangelii secundum Johannem, ch. XI: SC 151, 254).

Concerning the relation between the knowledge of God achieved by the observation of the natural world and the one derived by the faith in Scriptures, the Fathers of the Church offer some useful insights. Basil of Cesarea affirms: “Which is first: knowledge or faith? […] In our faith concerning God, the thought that God exists goes before, and this we gather from His works. We recognize by observation His wisdom and power and goodness and all His invisible attributes from the creation of the world.” (Epistula, 235, 1: PG 32, 872B). On the same subject, Tertullian: “We state that first we know God through nature and after we recognize Him in the doctrine. Knowledge through nature comes from His works; knowledge through doctrine, from preaching.” (Adversus Marcionem, I, 18: PL 2, 266). This same view can be found in John Paul II’s encyclical Fides et ratio (cf. n. 36).

Taking into account also the Patristic view on faith and reason, the leading ideas on the usage and implications of the metaphor in this period can be summarized as follows:

a) Within the cosmological argument, employed to infer the existence of the Logos, that is of God, from nature, the image of nature as a book given by God to men is clearly present. Creatures may be compared to letters, words or voices, but it is beyond question that God speaks to us, and reveals himself, through nature.

b) The Book of Nature is as universal as the Book of Scripture, and the content of each is to some extent equivalent. At times it transpires that the Book of Nature is even more universal and more comprehensible than the Book of Scripture. Creation is before everyone’s eyes, as a source for moral and spiritual appeal.

c) Knowledge of the Book of Nature seems to be relevant, and for some authors even necessary, to understanding correctly the Book of Scripture, for the knowledge acquired by observing and studying natural things precedes the knowledge of God’s revealed words.

d) With regard to moral and ethical dimensions, there is a strong analogy between moral natural law (i.e. moral commandments humans read in their heart) and the revealed divine law. The first is written by God in the world and in human conscience, the second is written by the same God in the Scriptures.

3. Authors of the Middle Ages: the case of Hugh of St. Victor and St. Bonaventure. The metaphor of the Two Books survives among the Christian authors of the Middle Ages; with theology continuing to inquire about the relationship existing between them. The study of the metaphor in the Islamic tradition is beyond our present scope. However, an overall look at the content of the Koran shows that the term “book” never refers explicitly to nature, but is always used to indicate the same Koran and its laws, that are seen as the book par excellence. Some Islamic authors have noted that the Koranic verses are called ayat (“signs”), as the phenomena of nature are, indicating that the Koran could be seen as the counterpart of a natural text translated into human words (cf. Nasr, 1996). An indirect reference to the difference between Christian and Islamic traditions is made by the Catechism of the Catholic Church, n. 108. Within Christian tradition, references to the Book of Nature can be found, with different nuances and to different degrees, in Bernard of Clairvaux (1090-1153), Hugh of St. Victor (1096-1141), Bonaventure of Bagnoregio (1217-1274), Thomas Aquinas (1225-1274), Thomas of Chobham (about 1255-1327), Dante Alighieri (1265-1321), Thomas of Kempis (1380-1471) and Raymond of Sebond (about 1385-1436), the subject of a next section (on the the Middle Ages, see Gellrich, 1985).

In this period, two authors deserve more attention: Hugh of St. Victor and Bonaventure. Both emphasize that the universal understanding of the Book of Nature is weakened by human sin. The Book of Scripture exerts a kind of “healing action” over the book of Nature: after the original fall, and because of our sins, to recognize God in the spectacle of nature is not an easy task to accomplish. Thus a “third” book comes forth, the book of the Cross. Christ himself, his Incarnation and his redemption, is compared with a great book, whose reading is necessary to the proper understanding of the other two books. To this respect, Jesus Christ seems to play quite an interesting, twofold role. He acts indeed like a hinge between the Two Books. When considered as increated Wisdom, he shows a special relationship with the Book of Scripture; when considered as the Incarnated Word, he is mainly associated to creation.

Hugh of St. Victor points out that to read the Book of Nature properly, one needs to have a spiritual, not merely a natural (that is material) attitude: “For this whole visible world is a book written by the finger of God, that is, created by divine power; and the individual creatures are as figures in it, not derived by human will but instituted by divine authority to show forth the wisdom of the invisible things of God. But just as some illiterate man who sees an open book looks at the figures but does not recognize the letters: just so the foolish natural man who does not perceive what pertains to the Spirit of God [cf. 1Cor 2:14]. He sees the form and the beauty outside creatures without understanding their inner meaning. On the contrary, the spiritual person can judge everything, and when looking at the beauty of the works, he soon realizes how the Creator’s wisdom has to be much more admired.” (Eruditiones Didascalicae, Book VII, ch. 4: PL 176, 814B). According to this mediaeval Master, God’s Wisdom is also a unique book, written inside (Holy Scripture) and outside (the works of creation). Nature is compared to a first scripture, the Bible to a second scripture. The Incarnation of the Word is a third scripture, which is seen as a book that also has an inner and an outer side, the first because of his invisible divinity, the second because of his visible humanity (cf. De sacramentis, Book I, Pars VI, ch. 5: PL 176, 266-267). All these images recall that book written on both sides which both the prophet Ezekiel and St. John’s Book of Revelation speak of (cf. Ez 2:9-10; Rev 5:1). In a work titled De Arca Noe Morali, Hugh of St. Victor speaks of three books and of three words, but with a different meaning. The first book or word is all what is made by human activity; the second book/word is creation made by God; and the third book/word is Wisdom himself, that is the Uncreated Word. In this case, Jesus Christ, as Incarnated Wisdom, plays the role of Sacred Scripture, of which he is the fulfilment (cf. De Arca Noe Morali, Book III, ch. XII, De tribus libris, and ch. XIII, De tribus verbis: PL 176, 643-644).

In the works of St. Bonaventure, the metaphor of the Book is widely used, so that expressions such as liber naturae, liber mundi, or liber creaturae, are synonyms for nature, world, creation (see, for instance, Itinerarium mentis in Deum, I, 14). At the same time, the necessity to know God through Sacred Scripture and not only through nature, and the demand for a third book, the book of Christ Redeemer, is nevertheless explicit. Here are two outstanding texts: “Before sin, man had the knowledge of created things and through their images he was led to know God, to praise, to worship and to love him. The purpose for which living beings exist, is to lead us to God. When human beings fell because of sin, they lost such knowledge and so there was no one who could bring all things back to God. Thus this book, that is the world, seemed dead and destroyed. Therefore, there was a need for another book through which the previous book had to be enlightened, in order to acknowledge the true meaning of things. This book is nothing but Sacred Scripture, which contains metaphors, images and teachings about the book of the world. In this way, the book of Scripture restores the whole world, and allows the latter again to lead us to know, to praise and to love God.” (Collationes in Hexäemeron, XIII, 12). “If we want to contemplate spiritual things, we need to take up the cross as if it were a book. [...] Christ himself is this book of wisdom, who is written inside by the Father, as he comes from the power of God, and outside, when he took on a bodily form. However, this book was open on the cross, and it is this book that we have to read in order to understand the depths of God’s wisdom.” (Sermones de Tempore, Feria VI in Parasceve, sermo II, n. II).

The Book of Scripture and the Book of the Cross, therefore, seem to have a kind of priority with respect to the Book of Nature, at least regarding our ability to clearly recognize God. However, Bonaventure does not deny the chronological priority of the Book of Nature over that of Scripture, as shown by this quote from the Breviloquium: “The first Principle is made known to us through Scriptures and creatures. Through the Book of Nature it shows itself as the principle of power; through the Book of Scripture as the principle of restoring. And since the restoring principle cannot be known without first knowing the principle of power, though the Bible tell us mainly about the work of redemption, it must also tell us about the work of creation». Despite the fact we are dealing here with a knowledge of nature through the pages of Scriptures, it is clear that such a knowledge calls for a comparison with the natural knowledge acquired by reason (cf. Breviloquium, Pars II, ch. 5).

Other passages of the Franciscan Master recall the image of the book written both inside and outside, an image that works at different levels. All things are like a book written outside, insofar as we confine ourselves to read them as merely effects of God’s power. Here is the step where natural philosophers seem to stop. Yet creatures are written inside, when we recognize them as traces or images (Lat. vestigia) of God. On a second level, material and irrational creatures are a book written on the outside, while rational and spiritual creatures, like humans and angels, are a book written on the inside, in the depth of their conscience (cf. Collationes in Hexämeron, XII; cf. also Breviloquium, ch. XII).

Thomas Aquinas seems to use the metaphor explicitly quite a few times, indeed if the research of the texts is confined to pick out only expressions such as liber naturae or liber creaturarum. One explicit reference can be found in Super Epistolam ad Romanos, ch. I, lect. 6; the image of the book appears also in two other works, Expositio in Apocalypsim, ch. 3 and Sermo V de Dominica secunda de Adventu, but their authenticity remains dubious. Nevertheless, it is worthwhile recalling that Aquinas provided a synthetic formulation of the relationship between the knowledge of God we acquire looking at nature, and the one we are taught by reading the Scriptures. With a sentence that will be quoted down through the centuries by many documents of the Catholic Church, he affirmed that natural reason is able to reach certain knowledge about spiritual realities, such as the existence of God, the immortality of the human soul, the existence of a moral responsibility before a provident Creator, etc.; however, God himself also wanted to reveal these same truths by the pages of the Holy Scripture, so that in this present condition of the human race, they can be readily known by all, with firm certitude and with no admixture of error (cf. Summa Theologiae, I, q. 1, a. 1. Aquinas’ doctrine is recalled by the First and by the Second Vatican Council, cf. Dei Filius, DH 3005 and Dei Verbum, n. 6).

To summarize, we can say that the Middle Ages introduce a certain theological realism in the question of the Two Books. Human reason is able to read the Book of Nature to ascend to God, but we have to take into account the wounds suffered by our intellect because of sin. This great Book continues to bind us to our Creator (cf. Bernard of Clairvaux, Sermones, De Diversis, IX, 1; Thomas of Chobham, Summa de arte praedicandi, ch. 7), but a spiritual and clear sight is required to recognize such a link (cf. Thomas of Kempis, Imitatio Christi, II, 4). Authors of the Middle Ages do not lose optimism, but seem to gain realism. Christian Authors now realize, by using the words of John Abbot of Ford (d. 1220), that “there is the book of creatures, the book of Scripture and the book of Grace.” (cf. Super extremam partem Cantici canticorum sermones, Sermo 104, 1). The Book of Nature does not lose its universality, but is framed within a strong christological perspective, and so demands other theological categories, such as Incarnation and redemption, fall and grace. Mediaeval Masters thus extend the metaphor of the book to Christ and to God. God himself, according to the beautiful verses of Dante’s Comedia, is the book, the volume, whose pages are scattered through the world, and which also allows Creation to be a book in itself: “In its depth I saw ingathered, bound by love in one single volume, that which is dispersed in leaves throughout the universe: substances and accidents and their relations, as though fused together in such a way that what I tell is but a simple light.” ([Nel suo profondo vidi che s’interna / legato con amore in un volume / ciò che per l’universo si squaderna: / sustanze e accidenti e lor costume / quasi conflati insieme, per tal modo / che ciò ch’io dico è un semplice lume], Commedia, Paradise, XXXIII, 85-90).

IV. The Renaissance and the dawn of the Modern Age

1. The influential Raymond of Sebond’s Liber creaturarum. As the Italian historian of science Lino Conti has shown (see Conti, 2004), at the root of the Modern Age’s view of the Book of Nature there is not only the spirit of the naturalistic Academies of the Renaissance, but also the very influential work of Raymond of Sebond (1385-1436) entitled Liber Creaturarum. A Catalan born scholar, Doctor in Medicine and Theology, Sebond was professor at Toulouse and president of that same University (1428-1435). The title of Sebond’s treatise changes a bit depending on the manuscripts existing in different European Libraries: Liber Naturae sive Creaturarum (Paris), Scientia Libri creaturarum seu Naturae et de Homine (Toulouse), Liber Creaturarum sive de Homine (Clermond-Ferrand), etc. The subtitle Theologia naturalis was added by the publishers, starting from its second printing in 1485. This book was remarkably successful: it had sixteen editions and many translations, including a French one made by Michel de Montaigne in 1569.  Until the beginning of the 18th century, various editors also re-arranged and re-organized the content of the book for different purposes (see, for instance, Regoli, 1789 and 1819).

The aim of the work is clear and explicit in the author’s Prologue: the knowledge of the book of Nature allows us to understand, in a true and infallible way, and without much effort, all truths about created things, man and God. The book of Nature tells us all that is necessary for our perfection and moral fulfilment, so that, by reading this Book, we can achieve our eternal salvation. Moreover – Sebond adds – it is thanks to the knowledge of the book of Nature that we can understand without error what is contained in the book of Scripture (cf. Sebond, 1966 reprint, Prologus, pp. 27*-28*). In the book of Nature each creature is nothing but a byte and a letter, written by the finger of God, such that all these letters and words together form a kind of manuscript, in which the human creature constitutes the most important word (cf. ibidem, pp. 35*-36*).

The relationship between the two Books is explained in detail but in a way that deviates, at least on some matters, from the teachings of the mediaeval Masters. Both books were given to us by the same and unique God; we received the first one from the creation of the world, while the second one was written thereafter. The book of Nature seems to have a certain priority, for it is said that our knowledge of it precedes and confirms the book of Scripture; it is like a door to enter the Bible and a light to illuminate its words (cf. ibidem, Titulus CCXI, p. 311). The knowledge of the book of Nature is available to everyone, while the book of Scripture can be read only by clerics. Nevertheless, the book of Scripture was inspired and written to help us read the book of creatures properly, since we were like the blind (cf. ibidem, Prologus, p. 38*) — a consideration that certainly refers to human sins and brings Sebond closer to the theologians of the Middle Ages. With an epistemological optimism that would have certainly amazed many contemporary philosophers of science, Sebond says that we cannot falsify or misinterpret the book of Nature, adding that, when studying it, there is no room for heretics or heresies. Contrary to Scripture, Nature cannot be deleted nor lost (cf. ibidem, pp. 36*-37*). We need both books and they do not contradict each other. They do not differ in their content: all that is present in the first, we also find in the second. They differ with regard to the way in which such content is taught and proved: the book of Creatures teaches by means of a rational demonstration (Lat. per modum probationis), while the Holy Scriptures are based on God’s authority and they teach us by means of prescriptions, commands and exhortations (Lat. per modum praecepti, mandati, monitionis et exhortationis) (cf. ibidem, Titulus CCXII, pp. 314-315).

Raymond Sebond strives to keep his balance, but the matter is delicate and somewhat critical. The risk of over-evaluating the book of Nature at the expense of the sacred Scripture is real; one could think, for example, that all of what is contained in the Bible can be known simply looking at creatures. It is true that he emphasizes in many places that the book of Scripture is “greater and higher” than that of Nature, because to speak with the authority of God is superior than demonstrating something by human reason: However, some of the arguments brought about by Sebond are precarious, and at times ambiguous. Trying to summarize his thought, we could say that from a cognitive point of view, the book of Nature is primary and more fundamental: its knowledge is more universal and con-natural to us, that is tailor-made for the human mind (cf. ibidem, Prologus, p. 37*); from the point of view of dignity, the book of Scripture has a higher value, because of the authority on which words contained therein are based (cf. ibidem, Titulus CCXV, pp. 322-324). Yet, the priority of Nature serves the Scriptures, because it is directed to the knowledge of the latter: thus all matter is counterbalanced once again, and Sebond finds his way once more (cf. ibidem, Titulus CCXII, p. 315).

It is no surprise that the doctrine of the Liber Creaturarum was interpreted and judged in different and sometimes contrasting ways. Some scholars saw in it the danger of reducing the significance of Scripture and weakening the authority of the Church to interpret it. Others saw in the work of Raymond Sebond a nice example of natural theology, in tune with the Christian philosophy of the Early Centuries and the Middle Ages. Among those who appraised Sebond’s work, we find: Nicholas of Kues, Hugo Grotius, Blaise Pascal, Peter Canisio, Franciscus of Sales, Georg Wilhelm Hegel. However, because of the implicit problems it contained, in 1559 the book was included by Pope Paul IV on the Index of forbidden books. But a few years later, in 1564, Pope Pius IV limited the prohibition to the Prologue only, asking that a note of theological clarification be inserted in all the later publications of the book.

Beyond the course of events and opinions related to the work of Sebond, there is no doubt that the content of the Liber Creaturarum differs somewhat from the theological perspective held during the Middle Ages. For the first time – and probably beyond the intentions of its author – we find an attempt to read a moral doctrine in Nature in such a way that, in principle, the consideration of the sacred Scriptures could be left out. Now the book of Nature can be seen as a book autonomous in itself. It is probably from this point that the road was open for a “modern religion of nature”, one capable of conveying moral and spiritual values without a necessary reference to the revealed religion based on the Bible. This will give rise at least to a couple of philosophical lines of thought. The first consequence is a kind of “lay sacralization” of nature, different from those spiritual views of nature practiced by Scottus Eriugena, Celtic Christianity, Hildegard von Bingen or Franciscus of Assisi. A new natural lay religion can now emerge, having its own rites, prayers and moral prescriptions, which in the climate of Renaissance will come with the practice of magic. The second consequence is the possibility to see the relation between God, man and nature, minimizing the mystery of Incarnation and the history of salvation, thus preparing the deism of the Western Europe Enlightenment, a religion of reason and nature which leaves aside, and often criticizes, all the revealed religions.

2. Toward a breaking of the harmony. In the history of the image of the Two Books, Nature and Scripture, the XVII and XVIII centuries were the two centuries in which the meaning of the metaphor underwent the greatest conceptual and hermeneutical transformations. The Patristic and Mediaeval periods didn’t know a dialectic opposition between the two Books, although the search for an accomplished and reliable articulation between them remained a problem to be solved, as shown emblematically by Raymond of Sebond’s thought. It is worthwhile to note that, when approaching the Modern Age, the metaphor of the “mirror,” for which creation was still only a reflection of the divine sphere, is gradually disappearing, testifying that “nature” acquires a progressive and stronger autonomy. Nature is the source of its own meaning and light, without need to reflect the meaning and light of something else. However, non-conflicting views of the Two Books are well present in this period, as shown, among others, by authors such as Nicholas of Kues (1401-1464) or even Martin Luther (1483-1546).

It is an opinion shared by many scholars that it was Philippus Paracelsus (1493-1541) who first endorsed a view in which the Book of Nature came into conflict with other books, namely those of philosophers and theologians. All the books previous to the direct and careful study of nature lag behind: finally, the material world can be studied with new instruments, observed with method and rigor. Recalling the scientific and philosophical context in which the Academies operated, mainly indebted to Pythagoras, Plato and to mathematical approaches in general, among the books from which Paracelsus and his students wanted to keep their distance there were especially those by Aristotle, but also the works of Galen and of all the other Greek philosophers who authored a De rerum naturae. According to Paracelsus: “From the light of Nature must enlightenment come, that the text liber naturae be understood, without which enlightenment no philosopher nor natural scientist may be.” And one of his students will add: “Let the others read their compendiums, while we study in the great picture book which God has opened for us outdoors.” (cf. Curtius, 1990, p. 322; Peuckert, 1941, pp. 172-178). Henry Cornelius Agrippa of Nettesheim (1486-1535) maintained a similar thesis, stating in his work De incertitudine et vanitate scientiarum atque artium, that the Book of the Works of God now substituted the books of theology and philosophy. In these statements there is no direct reference against the Bible, but it clear that authorities other than observation and experience, when speaking of the natural world, must be put now on a secondary level.

Starting from the beginning of the XVI century, the Book of Scripture, which for philosophers and theologians was the main book, became a book among the others: the light to understand the Book of Nature must come only from nature, from our way of studying and observing it, not from other sources. In other words, we can approach the natural world without the mediation of sacred Scripture, of theology or scholastic philosophy, and of course without the mediation of any Church. What is at stake is not the existence of God: for the Renaissance scientists, it remains clear that God himself wrote the Book of Nature. The novelty, rather, is the “lay turn” now available to the XVI century naturalists: the world can be read directly, and then also the Architect and the Maker of the world can be praised and worshipped directly, that is, without mediation whatsoever. The agreement between natural philosophy and theology, between natural laws and revealed moral laws, ultimately between Nature and Scripture, an accord that was centered for a long time around the mystery of the two natures of the Incarnated Logos, human and divine, is bound to be broken. A “spiritual” reading of the book of Nature is still possible, but it is no longer Christian, as will be shown by the philosophy of the Enlightenment and by the spirit of Romanticism. Born in a Christian context, the concept of the world as a book now becomes secularized and ready to be alienated from its theological origin.

V. The metaphor of Book of Nature in the Modern Age

1. Galileo Galilei’s view of the Book of Nature. Because of his influence, it is now to the use of the metaphor by Galileo Galilei  that we must turn our attention. To be honest, in the works by Galileo Galilei (1564-1642) we do not find any sentence which states an explicit break between the Two Books; however, we find all the elements of a latent controversy.

As known, the most famous viewpoint of the Italian scientist is that the Book of Nature is written in a mathematical language. Its characters are triangles, circles and geometric figures: this is what he states in a well known page of The Assayer (1623). As a consequence, only the specialists of the natural sciences are capable of reading it, not exegetes nor theologians. This book can be read only by those who know that language. “Philosophy – he affirms – is written in this grand book, the universe, which stands continually open to our gaze. But the book cannot be understood unless one first learns to comprehend the language and read the letters in which it is composed. It is written in the language of mathematics, and its characters are triangles, circles and others geometric figures without which it is humanly impossible to understand a single word of it; without these, one wanders about in a dark labyrinth.” (cf. Galileo, Opere, vol. VI, p. 232. On the meaning of the mathematical language in Galileo’s works, see Palmerino, 2006). The metaphor appears again, with similar words, almost 20 years later, in the Letter to Fortunio Liceti (1641) where it seems enriched by a polemical vein. The ‘natural philosophers,’ he points out, stand out because they do not study nature through Aristotle’s books, but through scientific observations: “The book of philosophy is now that which stands perpetually open before our eyes; but because it is written in characters different from those of our alphabet, it cannot be read by everybody; and the characters of this book are triangles, squares, circles, spheres, cones, pyramids and other mathematical figures fittest for this sort of reading.” (Opere, vol. XVIII, p. 295). Therefore, the books employed up to that moment are outdated: the interpretation of nature is now entrusted to the method of “sensible and meaningful experiences” and to a language, mathematics and geometry, which avoids ambiguities, distinguishing appearance from reality. Nature and its study is a matter for natural philosophers, not for theologians (cf. Dialogue on the Two Chief Systems of the World, Dedica al Gran Duca, in Opere, vol. VII, p. 27).

The key-statements of Galileo’s view of the metaphor could be summarized as follows: a) God is certainly the same Author of the Two Books (cf. Copernican letters); b) Nature is written in the language of mathematics, and its characters are triangles, circles and others geometric figures; it can be read only by those who know this language (cf. The Assayer, 1623); c) Nature is the very object of natural philosophy: therefore a matter for scientists, not for theologians (cf. Dialogue on the Two Chief World Systems, 1632); d) The books on nature written or used by the cultural establishment of his time have now been surpassed by the book of nature, that is, by experimental knowledge (cf. Letter to Fortunio Liceti, 1641); e) Instead of backing each other on their own books, as philosophers do, it is much more reliable to back on the Book of Nature itself (cf. The Assayer, 1623).

It is worthwhile to point out that from the epoch of the Fathers of the Church the meaning of the metaphor is, in Galileo’s words, surprisingly overturned. If St. Augustine and other authors of the Patristic period stated that “everyone, even the illiterate, can read the book of the universe,” (cf. Enarrationes in Psalmos 45, 7: PL 36, 518), according to Galileo’s view, people qualified to read it now belong to a much narrower circle. Even Raymond of Sebond’s proposition that the knowledge of the Book of Nature is familiar to everyone, while the book of Scripture can be read only by the clerics, is here overturned. Nevertheless, the Italian scientist is still convinced that the “Two Books” are in agreement with each other, because God is their only author. The sacred Scriptures are written by the Holy Spirit, and Nature operates according to the orders received by the divine Word (cf. Letter to P. Benedetto Castelli, December 21, 1613, in Opere, vol. V, p. 282). However, Galileo’s view sets forth that the Two Books show a remarkable difference: the revealed truths were dictated by God in the Bible using human language, which remains limited and somewhat ambiguous, while the natural truths were written by God with the precise language of mathematics. On closer inspection, it is the limits of verbal language as such – when compared with mathematical and geometric languages – that Galileo seems to want to highlight in his Copernican letters, without reducing the authority of the revealed divine Word.

Galileo, then, did not use the Book of Nature against Scripture, but reaffirms the autonomy and self-consistency of the natural world. The ‘walls’ to protect the autonomy of nature are built restricting the language in which nature is written, so regulating the access to its proper domain. For the first time the readability of nature seems to lose its universality. While for the Fathers of the Church the obstacle to the reading of Nature’s book was the absence of contemplative spirit and humility, and while Mediaeval theologians emphasized the role of human sin, Galileo now points out that the true obstacle is just the ignorance of geometry and mathematics. The impediment to read nature properly is no longer the consequence of a moral cause, but the consequence of a defect in education.

Yet it should not be forgotten – and this is a point of the utmost importance – that such a change becomes possible because the different dimensions owned by the polysemic concept of ‘nature’ now rank according to a hierarchy different from the past. The aesthetic-contemplative dimension, which was the only one available to the Fathers of the Church and to the author of the Classical ages, is no longer the first to be grasped. This dimension/meaning does not disappear, but it requires a ‘supplement’ of reflection: the most important meanings that modern Scholars of nature now associate to their object of study are measurability, mathematization and experimentation. In other words, there is an important semantic shift between readability and mathematization, one that will have further repercussions. In fact, there is a conceptual difference between a natural phenomenon read as a page or as a letter in a book, and a natural phenomenon interpreted as (or thanks to) a mathematical formula. Even though the encrypted form of a natural phenomenon could be an object of contemplation – think, for a moment, to Maxwell’s equations of electromagnetic field – we don’t understand a mathematical formula by reading it, but by accepting its operativeness and its character of legality. Because of the gradual growth of mechanism, made possible by mathematization, natural realities are no longer read but rather analyzed and reproduced. The symbols that represent them, like those described by a formula, begin to express ‘our way of controlling’ those same realities. On an aesthetic and contemplative level, the room for God’s revelation in nature becomes increasingly thinner, unless we identify the Creator with the formulas, the Logos with a computer. If it is true that below the mathematical equations and the scientific laws there exist the ‘laws of nature,’ that is, a metaphysical substratum which grounds the readability of the Book and transcend any mathematization, it remains also true that, to bring this substratum to light, science is not enough and we need a ‘philosophy of nature.’

Concerning Galileo’s understanding of the metaphor, a last question must be addressed. The new reading he proposed, was it really a restrictive reading, theoretically based on Platonism (although Platonic mathematics has the criteria of universality and not of hermeticism), or was it rather a mere rhetorical stratagem? How much the Platonic root of mathematics is responsible for this change is, with regard to the history of our metaphor, not an easy problem to solve. The Platonic cosmos, we must not forget, is not a book: to know it, is not to words that one must go, but to ideas and memory. The very belief that the created world can be read has Christian roots and, as we tried to show in our first Lecture, rests on the theology of the Word. If Neo-platonism is able to capture the image of the book and leads its understanding, it is because of the ‘rationality’ that the metaphor expresses, rather than for the idea of ‘readability.’ The reasons for the success of the metaphor, which from Galileo onwards will accompany the scientific culture up to our days, seem to lie, above all, in the fact that it conveys very well the vision of a nature that had become an autonomous and consistent ‘source of study,’ a book open before the eyes of the observer, whose reading, like that of any other book, requires order, scrutiny and application. However, it must be noticed that mathematical language is not foreign to a dimension of universality. From Galileo onward, scientific activity is nothing but the work of those who discover ‘laws’ (whose etymology can still be traced back to one of the meanings of the Greek verb léghein), those who decipher a content, and then remain, at least in principle, capable of recognizing their Author. All these aspects will be present in the use of the metaphor made by men of science throughout the XVII century and for much of the XVIII century, even if the reference to the ‘second’ book, that of Scripture, will become increasingly implicit or even absent.

2. Some different perspectives co-existing along the Modern Age. The references to the metaphor, occasional or systematic, made by authors of the Modern Age, and related in some way to the activity of science, are quite numerous. Among the authors who speak of the Book of Nature we find Francis Bacon, Matteo Ricci, Edward Topsell, William Harvey, Thomas Browne, Johannes Kepler, Robert Boyle, George Berkeley. Moreover, there are works written for apologetic purposes by clerics, who were familiar with the sciences, whose title is inspired by the metaphor. It is the case of Noël Antoine Pluche, Spectacle de la Nature (1732) and John Toogood, The Book of Nature (1802). Similar views are present in the works by John Ray, William Derham and William Paley. Not a few number of authors endorse the view that creation should be considered ‘our first revelation’. Other authors, such as René Descartes, Balthasar Gracián and Federico Cesi, emphasize the role of the ‘Book of the world,’ that is, what we can learn travelling and by our own experience, opposed to the learning of traditional education entrusted to printed books and traditional rules.

Because of his scientific authority, the thought of Robert Boyle (1627-1691) is of special interest for us. The image of the book is well present in his last work, The Christian Virtuoso (1690), which contains his scientific and sapiential meditation. Referring to the method employed by scientific research, Boyle affirms that the book of Nature is a large and beautiful rolled tapestry that we cannot see all at once, but we must be content to wait for the discovery of its beauty and its symmetry, little by little, as it gradually unfolds showing itself more and more (cf. The Christian Virtuoso, Part II, proposition VI, aphorism XXI). In a short essay entitled Of the Study of the Booke of Nature, written between 1640 and 1650, Boyle mentions the wonders observed with a telescope (one he thought was superior to Galileo’s) and considers the celestial phenomena a revelation of God, a testimony to His greatness and wisdom. (cf. The Works of Robert Boyle, vol. 13, pp. 147-172). If nature is the place of the Creator’s revelation, then the scientist is a privileged recipient of this revelation, thanks to his sophisticated instruments and the deeper observations he can make. The scientist does not keep this divine revelation private, as if it were a kind of hermetic knowledge; instead, he has the responsibility to communicate it, to praise the Creator on behalf of all men, a kind of ‘priestly’ function that we will find explicit also in Johannes Kepler (1571-1630).

We find the metaphor also in another of Boyle’s work, entitled Some Considerations touching the Usefulness of Experimental Natural Philosophy (1663). Boyle is convinced that knowledge of the Book of Nature does not hinder the Christian faith, but rather favors it; to this end he does not promote naive concordisms, as the Physico-Theology movement will do short later, but he rightly maintains that the Christian virtues that illuminate the relationship with God, such as humility, gratitude, and reverence, are fostered by a deeper encounter with the works of the Creator, an encounter now promoted precisely by science. The great balance with which Boyle exposes the relationship between the two Books is surprising. On the one hand, the Book of Scripture is superior, because if the ‘naturalist’ contemplates many attributes of the Creator reflected in his works, there are still many and more important attributes, such as love and mercy, about which the Book of Nature is silent. On the other hand, in his work The Excellency of Theology compared with Natural Theology (1674), Boyle specifies that the study of Scripture is far from rendering the study of Nature superfluous: the ultimate truths revealed by God do not deprive the scientist of the joy of investigating the natural world, but instead drives him to devote himself to this activity with all his strength.

With regard to the readability of the Book of Nature, at least three different traditions seem to co-exist in the Modern Age. The first is that contained in works having an apologetic or theological-catechetical character, even if written by men of science (as in Boyle’s case). According to this first tradition, Nature is a public book, to which everyone has access. Following a second tradition, the book is still public, but precisely this openness is what renders Scriptures superfluous: it is the perspective of Deism. The third tradition, finally, having a naturalist and Neo-platonic character, affirms that the book is no longer public, and such a restriction is often associated with a polemic vein: it preserves the idea that only specialists, that is, ‘natural philosophers,’ can read this book. In this last case, the careful observation and study of nature is reserved for those who know the formal language of science, a terrain in which metaphysical philosophers and theologians wouldn’t know how to act properly. This third view is endorsed, for instance, by the Italian physician Giovanni Alfonso Borelli, admirer and follower of Galileo, founder of a school of medicine called “iatro-mathematics”. In his work De motu animalium (1679), Borelli tried to interpret the living beings by means of mechanism and mathematical interactions.

It is interesting to underline that many scientists of this epoch, especially those belonging to the Protestant cultural environment, propose ‘their own’ personal reading of Scriptures, without any worry of reconciling this direct reading, that is their own biblical exegesis, with any theological school or church. In so doing, the priests of the Book of Nature end up being priests also of the Book of Scripture. Galileo himself, in his Copernican Letters, although he intended to go back to the Fathers of the Church to justify the use of non-literal exegesis, presented to theologians his own exegetical solutions, not without argumentative deficiencies and some contradiction (see McMullin, 1998; Fabris 1986, pp. 43-44).

Different currents of thought also co-exist regarding the capability of human reason to read and understand the Book of Nature. For some authors, the role of sin (as for most of the Mediaeval authors) would prevent the recognition of the Creator starting from creatures; for others, the exaltation of reason and scientific knowledge inexorably migrates the metaphor towards the use that the deism of Enlightenment will make of it. For the latter, the Book of Nature will still show a character of universality: however, this is no longer the universality of God’s aesthetic and salvific appeal, but the universality of reason. Even if the term ‘God’ does not disappear, Samuel Reimarus (1694-1768) and other deists now replace the reading of the Book of Nature with every possible divine revelation: “God in his wisdom and goodness, if he wants to make all men blessed, cannot make necessary and unique means for bliss what is impossible for the vast majority of them to achieve; it follows that [supernatural] revelation must not be necessary, nor must man be made for revelation [...]. Therefore there remains only one way by which one thing can truly become universal: the language and the book of nature, the works of God and the traces of divine perfection that are clearly shown in them, as in a mirror, to all men, to the learned as to the unschooled, to the barbarians as to the Greeks, to the Jews as to the Christians, in all places and in all times.” (S. Reimarus, Apologie oder Schultzschrift für die vernüngtigen Vereher Gottes, in G.E. Lessing, Gesammelte Werke, ed. by P. Rilla [Berlin: Aufbau Verlag, 1954-1958], vol. VII, pp. 686-734, p. 734).

Here the idea that nature possesses a certain ‘redemptive’ value gradually consolidates. This vision will acquire both romantic and radical tones in J.-J. Rosseau. Already in the Middle Ages, despite a greater realism in judging reason wounded by sin, this idea was slowly coming into light. Hildegard of Bingen thought that learning from nature could even ‘restore’ a correct knowledge of things. Raymond of Sebond stated that the cognitive priority of the Book of Nature also had some moral consequences. For Boyle, the role of nature is at least ‘propaedeutic,’ because it educates to humility and to those other virtues necessary to understand biblical revelation and receive it fruitfully. For Edward Topsell, an Anglican priest and naturalist, the universal language of the Book of Nature would be able to recompose the fragmentation of human language caused by the confusion of Babel.

In the following course of history, and perhaps up to our era, the apologetic and catechetical use of the metaphor seems to have had a longer life compared to the Neo-platonic tradition and to the thought of deists. Many Christian authors will feed it, although not always equipped with enough scientific competence. They have often underlined the order and harmony of the Book, the intrinsic finalism of nature oriented to the service of man, the evidence of a Creator who has planned morphologies of the living beings and biological processes.
However, the naivety of some of their considerations, although endowed with a certain heuristic value, will make the break with Darwinism more severe and critical. This break occurs upon realizing that biological evolution and natural selection are also satisfactory causes for adequate morphogenesis and for the harmony between living beings and the environment.

However, the authors who set forth the Darwinian interpretation of nature and history didn’t realize that the image of the ‘Book’ would continue to have a value also within an evolutionary perspective: actually, the Latin term evolutio expresses the unfolding of the volumen, that is, of a book, the unrolling of the tapestry of nature —to use the metaphor employed by Robert Boyle. Pope Benedict XVI gave witness of this, on occasion of a speech to the Pontifical Academy of Sciences in 2008: “To ‘evolve’ literally means ‘to unroll a scroll,’ that is, to read a book. The imagery of nature as a book has its roots in Christianity and has been held dear by many scientists. […] It is a book whose history, whose evolution, whose ‘writing’ and meaning, we ‘read’ according to the different approaches of the sciences, while all the time presupposing the foundational presence of the author who has wished to reveal himself therein. This image also helps us to understand that the world, far from originating out of chaos, resembles an ordered book; it is a cosmos. Notwithstanding elements of the irrational, chaotic and the destructive in the long processes of change in the cosmos, matter as such is ‘legible’.” (Benedict XVI, Discourse to the Pontifical Academy of Sciences, October 31, 2008).

A remarkable change of perspective occurs with the rise of German idealist romanticism. Many of the contents associated with the concept of nature are now shifted into the concept of history. It is true, of course, that the encounter between the metaphor and the scientific environment, two or three centuries earlier, had already produced its fruits. That is, it has conferred authority, autonomy and rigour to the study of the natural sciences. However, from the XIX century onward, both nature and human life will be seen primarily as history, as the Bible will be. The true way to seeing at nature is historically. Nature itself is a history. Consequently, the world of books is considered only the parody of the real world, and the metaphor of nature as a book loses interest. Nature has its own story to tell, the ‘natural story,’ and it does so using the material and findings that the scientist collects, observes, reads and deciphers, just as the historian does using his documents. From the comparison between ‘Two Books’ we shift to the comparison between ‘Two stories,’ the history of the natural cosmos and the history of biblical salvation. Contemporary theology has then inherited the task of showing, not without labor, how these two stories are two readings of a single history, at the center of which, as in the metaphor of the Two Books, lies the mystery of the Incarnate Word.

VI. Science, theology and the future of the metaphor

1. A heritage to be appraised. Are all these difficulties and subtle clarifications strong enough to prevent today’s science and theology dialogue from speaking fruitfully of Nature as a book written by God? If we don’t want to use the adjective ‘ambiguous,’ we should at least acknowledge that the metaphor is a multifeatured image, having different meanings. In addition, the tricky and problematic heritage of the very concept of ‘nature,’ one of the most complex subject-matters in all the history of ideas, brings more troubles to an already problematic issue. Looking at the history of metaphor, we find at least four different ways of referring to the Book of Nature. They are in turn:

a) Thanks to this book, the knowledge of the Creator, of whom biblical revelation speaks about, is extended to all, in a very accessible way, making known to all the fundamental moral requirements that derive from the existence of a Creator; Nature is therefore proposed as a true form of divine revelation, comprehensible, effective and universal.

b) This book confirms the reasonableness of the religious and moral teachings contained in Sacred Scripture, showing that these are also available to those who observe the natural order of things and the laws which rule it. The image of the ‘Two Books,’ then, stresses the uniqueness of their Author.

c) This book shows the self-sufficiency of a natural moral order with respect to the teachings contained in biblical revelation, bracketing out the latter, or declaring it superfluous.

d) The Book of Nature, finally, indicates a field of competence reserved only for the scholars of the natural sciences, because of the specific and restrictive language in which the book is written; the image of the ‘Two Books,’ can even express a break between the rational and mathematical study of the world, and the view of creation given by philosophy, theology, or by the Bible itself.

At the same time, notwithstanding the complex history of the metaphor and the different meanings it has acquired, it should be regarded as a rich heritage to be appraised. Actually, it brings about a number of interesting insights which could nurture science and theology dialogue. These insights appear to resist the different hermeneutical views proposed, and they stand above the contrasting purposes with which the image has been used. Actually, three main ideas seem to persist through history, shared by most of the authors: a) the Book of Nature is universal (the language of mathematics, in a sense, continues to express a dimension of universality); b) it has an Author (other images of nature, as ‘mother,’ or ‘living being,’ etc., do not primarily refer to any author); c) the image has been widely used by scientists because it has many things to say to the activity of science, in the past as in the present. Let’s comment on each of these ideas, in turn.

First, the idea that nature is in front of our eyes like an open book, a public book that everyone can read, even if not everyone knows how to interpret it immediately, is a content that persists through all epochs with different emphasis. The sky is above all of us, the earth is under the eyes of all. Everyone comes across nature, because it is our common home. We need not look for this book, because it comes to meet us. Somehow it reveals itself. It speaks to someone with its illustrations, to others with its arguments, to still others with its laws, whether of a physical or moral order. On closer inspection, even if we were to recognize that it is written in mathematical characters and think its reading reserved only for those who know its language, we would not deny its universality. Rationality and science still have a public dimension because everyone, in principle, can be educated to have access to this knowledge. In contemporary society, where the suggestion of the unknown and the search for secret mysteries too often replace the true religious sense, the call to the universality of divine revelation in a book available to all can help to avoid this dangerous drift. And in this task science and theology find themselves on the same side, because they are both interested in reason, that is, in the Logos that grounds the Book’s readability.

Second, those who have used for centuries the metaphor of nature as a book, or also the metaphor of the ‘Two Books’ including sacred Scripture, they all have accepted, at least implicitly, the possibility of thinking of a personal Author. For the materialist and the atheist, closed to any possible transcendence, nature is certainly not a book, but only a place of conflict and irrationality, the theatre of pure chance, something which looks absurd. Knowing the reasons why the metaphor has been used would allow theology to better understand where and why implicit or explicit references to an Author of the Book were born, helping the interlocutor (including scientists) to evaluate which Subjects are philosophically adequate to play the role of an intelligent and personal author. It should be noticed that the reference to the ‘author’ was not denied even by those who emphasized the self-sufficiency of the Book or defended the autonomy of scientific work. Until the rise of XIX century materialism, none of these prerogatives of nature was affirmed against the existence of God. Within the rich framework of the metaphor, theology could help scientists to recognize the many consequences which stem from the belief that in the very foundation of physical reality there is a personal author. Because the writer is personal, the universe is readable, it is rational and lawful, it conveys a message and embodies a purpose. In a word, it reflects what a book is and what a book means.

Third and last, the dialogue between theology and the natural sciences can be fostered by the historical fecundity of the metaphor of the ‘two Books’ – albeit within the limits and the hermeneutical warnings already highlighted. Contrary to a rather widespread cliché, the scientific revolution did not mark a break between the Two Books, but rather gave voice to a need for a greater intelligibility of both. There is a consolidated tradition, even among the witnesses of the newborn scientific method, from Francis Bacon to Tommaso Campanella, from Galileo Galilei to Robert Boyle, according to which the Book of Nature helps the understanding of the Book of Scripture, and the latter remains unchanged in its moral and spiritual value for our lives. Precisely because the author of the Two Books was the same, with the development of the sciences new interdisciplinary questions arose and new implications came to light. These not only concerned, evidently, biblical exegesis, but creation as a whole, which to scientific observations now appeared with an extent, richness and complexity previously unimaginable. Scientific discoveries claimed – and in a certain way will always ask for – a re-reading of the Book of Scripture. Beyond the inaccuracies and misunderstandings that the Copernican revolution showed on both sides, the call that Galileo addressed to theologians will be addressed by other men of science in the following centuries, on new important issues, from Darwin to Freud. At the same time also Scripture can also encourage scientists to read the Book of Nature again and read it better; in so doing, theology and Scripture do not interfere with the scientific method, but help them distinguishing what in that Book speaks to science and what, instead, speaks to the existential and religious dimensions of the human being, what is written in the characters of mathematics and what, instead, is written in the language of wisdom. A scientist like Robert Boyle, for example, was able to read Nature according to this two-fold appeal, showing how each reading complemented the other.

All these reasons suggest that a theology operating in a scientific context like ours, should appraise all the richness that the metaphor still has, and use it fruitfully (see Tanzella-Nitti, 2018, pp. 360-394). However, to put this program in practice it is necessary that among their studies theologians include also a good reading of the Book of Nature, incorporating in their curricula some knowledge of the natural sciences. Due to many reasons, most of contemporary theologians have lost the familiarity that the clergy of the past centuries had with the results, and even with the practice, of the natural sciences. It is only thanks to a better knowledge of nature that they could understand – and explain in a convincing way – how and why natural history and the history of salvation are part of the one and the same history. With regard to this need, Tommaso Campanella used very lively tones in his Apologia pro Galileo (1622), a writing which makes also a wide use of our metaphor of the book. Invoking Augustine and Thomas Aquinas as witnesses, he recalls that in the Christian faith human reason finds itself at home; so it must continue to be, because “those who prohibit Christians from studying philosophy and the sciences, prohibit them also from being Christians.” (T. Campanella, Apologia pro Galileo, Typis Erasmi Kempfferi, Francofurti, 1622, p. 14).

2. Science and information: a contemporary look at nature. Despite the passing of the centuries and the change of philosophical paradigms, scientists continue to approach Nature  according to the image of something that must be read or listen to. Some of them speak of their research activity as a sort of ‘dialogue’ between themselves and nature, and of their discoveries as an experience of ‘revelation.’ According to John Polkinghorne, “Physicists laboriously master mathematical techniques because experience has shown that they provide the best, indeed the only, way to understand the physical world. We choose that language because it is the one that is being “spoken” to us by the cosmos.” (J. Polkinghorne, One World. The Interaction of Science and Theology [Princeton: Princeton University Press, 1987], p. 46). Edwin Hubble saw nature as an appealing partner which startles the scientist: “Sometimes, through a strong, compelling experience of mystical insight, a man knows beyond the shadow of doubt that he has been in touch with a reality that lies behind mere phenomena. He himself is completely convinced, but he cannot communicate the certainty. It is a private revelation.” (E. Hubble, The Nature of Science and Other Lectures, San Marino (CA) 1954, quoted in O. Pedersen, “Christian belief and the Fascination of Science,” Physics, Philosophy and Theology. A Common Quest for Understanding, edited by R. Russell, W.R. Stoeger, G.V. Coyne [Vatican City: LEV and University of Notre Dame Press, 1988], p. 133).

As scientific knowledge goes forward, we do not know what future is reserved for the metaphor of the Book of Nature. At a time when the book has become a digital document and its readability has become that of a binary code, science gladly speaks of ‘cosmic code,’ making the image of the book migrate towards that of a computer program. The idea of a ‘numeric code,’ for instance, seems to emerge when cosmology reflects upon the delicate fine tuning of the numerical constants which rule the strength of the fundamental laws of nature expressed by the Anthropic principle. The idea of a formal code is also present when biology reflects on the structure and meaning of the DNA molecule, or when looking at a living organism as the result of a complex and ordered system of interrelations. This new metaphor would make the problem of the language in which the book is written even more severe, and its accessibility more restricted. However, also if these were the winning metaphors of the future, theology would not lack opportunities for dialoguing with the sciences. On this point, it is meaningful to recall that Francis Collins, the scientist who directed the “Genome Project” for the coding of the human genome, felt the need to write a book about DNA coding entitled precisely The Language of God (2006), and he gave rise, just after his conversion from agnosticism to Christianity, to a Foundation for interdisciplinary research on science and faith called ‘Bio-Logos.’

A promising way to continue the science and theology dialogue on the readability of nature is to highlight the philosophical dimensions contained in the powerful notion of information, as it is employed by contemporary science. Universe and life are made by matter, energy, and information: a meaningful question, then, is to ask where information comes from. Information seems to rule both the structure and evolution of the universe as a whole, and the properties of each single material entity as such. It is thanks to information that all things, from quarks to galaxies, are the way they are and not otherwise. The theological notion of Logos, which is at the basis of the legibility of nature and historically gave rise to the metaphor of the book, is still available to enlighten what information is, in the structure of the universe and in the constitution of life. The dialogue between science and theology on the meaningful notion of information can be nurtured and clarified by a philosophy of nature able to show the role of ‘formal causality.’ Unlike final causality, which could be seen by scientists with suspicion when presented as something extrinsic to scientific method, formal causality is intrinsic to empiric analysis, because quantitative dimensions of material entities must rely upon their specific properties and qualities; these are nothing but their philosophical forms. The three historically persisting ideas related to the image of the ‘book,’ namely universality, reference to an Author, and relevance to science, are still valid when we speak of ‘information.’ Also in this case the metaphor of the book, which is precisely what conveys information, would continue to work, and the readability of nature will continue to evoke wonder.