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The Universe as a Philosophical Problem
The a priori assumptions of cosmology
Let us now consider other a priori assumptions of a different kind, which are indispensable when we try to speak of the past history of the universe, and in particular of its origins. The first of these assumptions is that we implicitly postulate that physical laws and principles, which we consider valid at present, were also valid in the past. At a first glance, this presupposition seems to be the same as is made in usual science, when we tacitly assume the invariance with respect to time of our laws and principles (in fact no scientific inquiry would be possible without such an epistemological presupposition). However we want to lay stress on the different kind of foundation this presuppostion receives in the two cases. In our "usual" practice - as we have been told by a long empiricist tradition - we are led to be confident that a certain law or principle "having been found valid in the past" should continue to be valid also in the future. But in the case of retrodicting the history of the universe, we cannot repeat this claim, since that these laws and principles "have been valid in the past" is just the question at issue. Therefore all the weakness of the empiricist foundation emerges here: the real situation is that we make such claims not on the basis of an experience of a necessarily very short duration (which can actually be qualified as a "present expe rience"), but on some other a priori ground, the most common of which has traditionally been the belief in the uniformity of Nature. In cosmology this presupposition of the uniformity of Nature is disguised in the form of different isotropy and homogeneity postulates, of which it would certainly be arbitrary to say that they are empirically grounded, since the empirical evidence is always very limited and, if we should take it seriously, it would rather speak against isotropy. Only by introducing very strong idealizations we can postulate these isotropies.
This is not illegitimate, provided we are aware that we are introducing in this way certain "conditions of intelligibility" which are of a philosophical nature and cannot be justified on purely physical grounds. Indeed, they move in a way in a direction contrary to that of modern physical science, which has been characterized by an ever-greater stressing of the locality of definitions and laws, owing to their operational anchorage. The explicit recovery of these requirements of isotropy and homogeneity (which were implicitly admitted in traditional physics) is an interesting confirmation of the philosophical horizon of generality which comes, in cosmology, to complement purely physical ways of reasoning.
The philosophical features of cosmology
It would not be difficult to mention other issues of a similar nature, but what we have said is enough for the purpose of our discussion. Let us then ask: does all this mean that cosmological investigations, and in particular investigations regarding the origin of the universe, are self-defeating, circular or incorrect? Not at all. It simply corresponds to the fact that when tackling such questions we are confronted with the particular problems bound to the "point of view of the whole", a point of view that science usually tends to remove, but which has an almost invincible tendency to reappear, simply because the whole inevitably constitutes the background and framework of all our knowledge. In fact, we can never have a single experience without conceiving it as being part of a whole: we have an awareness of this experience as constituting a certain focussing on a detail which belongs to a much broader structure, within which it occupies a certain place (in a very broad sense of this term). It is the presence of this global horizon which provides us with the possibility of making the single items of our experience intelligible.
Modern science has been characterized, among other ways, by the fact that it puts limitations on this aspiration towards the whole, through a double attitude. Firstly, by claiming that a correct and satisfactory knowledge of the details, of the parts, of the particular aspects, may be attained without presupposing an understanding of the whole. We may call this the "Galilean prerequisite", since it was Galileo who explicitly proposed the delimitation of natural investigation to a restricted set of empirically ascertainable features or properties of things and, moreover, introduced a kind of tripartition among an observed physical system, the observer, and the rest of the world. He assumed that a satisfactory and objective knowledge of a physical system was possible without taking into account either the observer, or the rest of the world (which in this context maymean the "whole" which is considered to be irrelevant to the scientific investigation of an isolated system). Here, by the way, it is possible to see the origin of the principle of locality, which remained basic to physics until the advent of quantum theory.
Secondly, modern science assumed that, when the consideration of complex systems is needed (systems which in this sense may be considered as being "wholes" with respect to their "parts" or constituents), an understanding and an explanation of the whole simply consists in an understanding of the functioning of its parts or constituents: it will "result" from their combination, according to the laws and principles regulating them.
It is probably correct to say that the combination of these two attitudes constitutes the substance of the analytic approach.
Under the first point of view it makes the intellectual problematization of the whole completely illegitimate, while under the second point of view it gives to this enterprise a limited legitimacy by indicating the particular conditions for its pursuit. Cosmology is in a way the expression of this kind of legitimation, and of the conditions under which it is admitted to be scientifically acceptable. In particular, cosmology is an expression of that methodological choice which we have already stressed above, i.e. that of availing itself of existing physical theories (which are necessarily "partial" and even "local" in the already specified sense), and trying to draw from them a satisfactory theory of that "whole" which is the universe. However (as we have remarked on that occasion) this strategy may at best provide a certain description and hermeneutic "comprehension" of this whole, without leading to a genuine nomological theory of it.
But the problems which we have just discussed above indicate that even this enterprise cannot be pursued without the intervention of some a priori element, and this is a symptom of the fact just mentioned, that the whole is "already there" when we engage in acquiring knowledge, and that we cannot help developing our knowledge according to our conceptions of this whole, which are implicit even in our analytic work.
Since philosophy is typically the intellectual attitude which aims at coping with this effort to understand the whole, it is not difficult to see that the presuppostions we have indicated are typical philosophical presuppostions, and that they play an especially important role when science is willing to confront itself with the problem of understanding the whole. For that reason we must say that the very concept of the Universe is a typical philosophical concept, and the fact that science has brought it under its scrutiny necessarily brings science to that interplay with philosophy, which it had known at the beginning, but which has been thought to have been dismissed in more recent times.
A confirmation of the above general remarks comes from everal particular considerations. The first is the well known difficulty of defining the universe as an "object", a condition which seems indispensable in order for cosmology to be a "science of something", but one which is hard to fulfill. If we take a definition of the sort introduced e.g. by Bondi, according to which «the Universe... is the largest set of all physically significant objects,» we meet logical problems and paradoxical consequences. If we try to escape them by defining the universe as the «reference set of a certain cosmological model», to we avoid formal inconsistencies, but are immediately confronted with the problem of knowing whether our model really captures the whole, i.e. the universe, or whether it is only the model of a very large and complex structure of objects belonging to the universe, but not exhausting the universe itself. In other words the idea of unity and totality which is the truly formal characteristic of the concept of the universe (in the classical sense of "formal") seems to be too primitive to be captured by explicit scientific definitions. We have already hinted at this fact, and have also hinted at what seems to be the fundamental reason for it, i.e. that a very special kind of "infinity" is involved here. In fact one's spontaneous impression could be that the logical difficulty in conceiving of the universe as the "totality of objects" resides in the impossibility of even theoretically encompassing such a totality, which is at least indefinite, if not actually infinite. However this is not the major problem: when we speak of an object of inquiry, we mean a "thing" considered under a specific "point of view", and since the points of view from which a thing may be considered are potentially infinite, we see that if the universe were to contain the totality of "objects", it would already be potentially infinite even if it contained just one thing. Of course, if it is meant to contain at the same time all things and all objects, the problem of grasping it becomes truly desperate.
Moreover, the consideration of this "whole" implies the violation of the "Galilean prerequisite" indicated above, since not only the single physical systems, but also the observer and the rest of the world must necessarily be included in the universe if it is really to be "the whole". This seems to be actually fulfilled by contemporary cosmology, which (tacitly) includes in particular a theory of the origin of life and the usual evolutionary theories of the origin of man under its umbrella. However this is no answer to our difficulty, since this amounts to including other people among the objects of inquiry, but does not eliminate the peculiarity of the "observer" and of its subjectivity, which remains hidden in the most delicate epistemological features of cosmology. The most notable of these features is the use of the concept of historical time, involving the notions of past, present and future, which are not objective in the sense of being intrinsic to the objects, but have a meaning only with reference to a conscious subject who says «now.». If one considers this point attentively, one might think that the anthropic principle, which introduces the consideration of human consciousness into cosmology in a way which seems gratuitous and extrinsic to many scholars, is perhaps far from being so alien to the epistemological background of this discipline.
Boundaries with metaphysics
The problems we have tackled lead us to ask the general question: «How can one try to understand the "whole"?» Since the whole is obviously not the content of any possible experience, but, as we have already seen, the implicit background which makes all experience possible, it cannot be the object of any direct empirical investigation. This remark seems definitely to condemn cosmology to providing pseudo-knowledge. However if understanding of the whole were to be conceived this way, not only cosmology, but also philosophy would be condemned as an illusory enterprise. But this is not so, simply because the whole is not to be understood as the "totality of the real", i.e. as the actual cumulative set of all existing individuals, with all their features and properties. It is obvious that if philosophy were to pretend to know the totality of the real, it would deserve the scorning irony with which its enemies often consider it. But philosophers are not unintelligent, ambitious people who believe themselves to be able to know al things and all properties of things by simply speculating or reading other philosophers books. Philosophy tries rather to understand the "whole" in the sense of elaborating and analyzing those most general concepts and principles of reality which could help us to understand it in the diversity of all its aspects, and this hopefully by finding a few concepts and principles of great generality, which is not a foolish programme, after all.
How this task can be carried out is among the most debated issues of philosophy, and we shall certainly not take it up here.
Rather, we shall content ourselves with saying that a solution of this issue which we are inclined to accept, and which is also well in keeping with scientific practice, is that this investigation of the whole is realized as an ideal reconstruction which starts from actual experience, and generalize principles and criteria of intelligibility which prove successful in some restricted field, but at the same time seem to be successful because they have a universal purport. (Whether these principles are abstracted from experience in an Aristotelian manner, or are Platonically inborn, or a priori in a formal Kantian sense, may be left undecided here).
What is important in this procedure is that the consequences of applying these general principles may lead one also to include into the whole (understood this time as the "totality of the real") entities which are not included in the empirical evidence in which the general principles themselves had been used at first, and this because they are meant to be principles of the whole, and therefore be susceptible of indefinite application. This use of principles and concepts we may call the synthetic use ofreason, to contrast it with the analytic use of which we have already spoken.
The move just described is typical of metaphysics, but it is also made in science. Every science tries to provide a complete account of its field of inquiry, and this means several things: the possibility or even the necessity of introducing theoretical entities, besides those which are empirically discovered and described using the empirical means admitted by that science; the unrestricted application of these general principles, which implies not only their indifference with respect to particular or accidental properties of the individual entities to which they apply, but also the possibility of applying them to cover the whole field of inquiry both synchronically (which practically means with respect to every region of space at a given time), and diachronically (which means with respect to all possible time instants). In such a way we see that the homogeneity and isotropy of time and space are already implicit in this "point of view of the whole" which we find both in metaphysics and in the most general intellectual attitude of science as well.
Is the consideration of past and future, and in particular the problem of the "origin", included in this approach? Not necessarily. In the case of the sciences, since it is already clear from the beginning that each of them concentrates its investigation on a circumscribed whole, it is tacitly admitted that the "rest of the real" (in many senses which we shall not mention here) remains out of consideration, so that the problem of the origin does not really surface. For example, biology takes life as given without asking from where it comes, chemistry does the same with material substances, physics with matter, energy, particles, fields. However it is not impossible (and it actually happens) that questions about these origins be asked, but then they are not scientific, but philosophical questions and, more precisely, cosmological questions, even though they are not necessarily formulated in cosmology proper. So,for example, the question of the origin of life is of a cosmological nature, since it does not properly concern "what life is" (a problem, in a way, for biology), but "what the place of life is in the whole", and this may be seen as a metaphysical question if this whole is understood with the greatest of generality, and as a cosmological question if the whole is understood rather as the whole of Nature.
We have seen therefore that cosmological questions are philosophical questions by their very nature. However, one can try to answer them by resorting to scientific knowledge. So, to take our example, one may try to answer the question of the origin of life by going back to chemistry, and then answer the problem of the constitution of the chemical elements by going back to physics. And then? Is physics the ultimate ground for solving the problem of the origin? The answer is delicate: a problem does not change in nature simply because we resort to some particular tools for solving it, and in this sense a cosmological problem remains philosophical in spite of being studied with the aid of a science. On the other hand, one may be convinced that physics does actually provide the solution to this problem, or at least that it is the only discipline competent to provide a possible solution: in this case one simply endows physics with the competence necessary to treat of the whole in the fullest sense of this term, and this is tantamount to making of it a metaphysics. This view is not in itself absurd, but it should be supported by showing that physical concepts and physical theories are independent of extraphysical a priori presuppositions, and have an unrestricted and allembracing validity. But this is just what has been shown to be problematic throughout this paper.
Without repeating now things which we have already hinted at, let us simply stress that all the drastic extrapolations which are usual and indispensable in cosmology have the character of metaphysical generalizations, even though the whole to which they are extended simply is the "whole of Nature". The most instructive example of this is the already discussed fact that local physical laws are assumed to be valid "everywhere and at every time": this seems to rely on the assumption of a cosmic uniformity which might be more or less justifiable on the basis of what we empirically know of the accessible universe, but a little reflection is sufficient to see that it is the admission of the unrestricted validity of these laws which actually defines the meaning of this cosmic uniformity. For that reason we must say that these laws play the role of non-local principles in a sense that does not coincide with the usual physical meaning of non-locality, but rather corresponds exactly to the classical requirement of universality and necessity, which is the distinguishing mark of the metaphysical principles.
That this is so is confirmed by the fact that these laws are assumed to be determined with a practically infinite degree of accuracy, otherwise even an accidental variation in the conditions of application, which could correctly be considered to be negligible from a local point of view, would result in total unreliability from the point of view of the cosmic consequences we should draw from this application (see what we have already said concerning cosmological retrodictions). Now, such an exactness beyond any margin of error is again a typical mark of the metaphysical principles, and is alien to the very concept of a physical law.
Another circumstance that is rather surprising, if we consider it from the point of view of standard scientific methodology, but which is in keepingwith the metaphysical way of reasoning, is that the physical laws in question have to be invariant not only, in a generic sense, with respect to time and space, but also with respect to the evolution of the universe. This point is crucial because it shows rather clearly that cosmic uniformity was not really a necessary presupposition for the extrapolation of the local physical laws, as it may have seemed to be when one simply considered space and time. Indeed, these laws appear now to be valid even in spite of a deep non-uniformity, i.e. in spite of their field of appli cation (the concrete universe) becoming radically different in the different stages of its evolution: they are not only "spacetime invariant", but even "evolution-invariant". Moreover, they are such that they remain independent of the evolution of the universe and at the same time predict such an evolution. From this point of view they share again the nature of the metaphysical principles, which are meant to explain mutation and change, and even to predict it, because they are valid independently of change, because they have an immutable nature. Morever it is essentially because of this feature that they are meta-empirical, since change dominates the empirical realm; and if they are so, no wonder that they are not subject to the conditions of space, time, change, uniformity or non-uniformity, etc. These conditions characterize the empirical, concrete, material world, but not the world of rea son. The attribution of the said invariances to the metaphysical principles is therefore a clear indication of their being principles of rationality, and to the extent that physical laws are endowed with similar invariances, they are promoted to the level of being rational, in the sense of being what is specifically meta-empirical.
We shall terminate our discussion of this point by indicating a final consideration, which corroborates the above-sketched view. Even attributing to known physical laws the metaphysical features just mentioned, several difficulties still remain in cosmological theories. How does one try to remove them? Sometimes by introducing new theoretical principles, but even by metaempirically postulating certain factual conditions which are in turn not justifiable within the theory which assumes them. Among the difficulties, or at least, as we have seen in part, among the "open questions" of the standard cosmological model, are zerocurvature, the causality paradox, the horizon structure, isotropy and homogeneity; and a merit of the inflationary model is that it can solve these problems. This model however relies upon two conjectures: that our uniform visible universe is the result of the expansion of a quantity of matter occupying a region of the order of 1030 em, an expansion which began when the universe was just 1035sec. old; that on this almost vanishing scale of length no chaotic substructure was present in space, so that this "smoothness" could evolve to the (alleged) smoothness of our observable world, thanks to the action of antigravity. It is easily seen that these two hypotheses are genuinely untestable factual assumptions of a synthetic character, for which no other justification is provided in the theory than the fact that they solve certain theoretical open questions. Here again we find the features of the synthetic use of reason which is typical of metaphysics.
A separate, but no less significant, case is constituted by the direct use in cosmology of expressions which are verbally identical to certain metaphysical formulations in the strongest and even most debated sense of metaphysics. We refer here, e.g., to concepts such as those of "genesis" and of "creation out of nothing" which are used in contemporary quantum cosmology for interpreting certain theoretical (or mathematical) results. In order to avoid any genuinely metaphysical interpretations of these expressions one may try to point out, first, that they are not inescapable, since it is not absolutely certain that GTR (within the framework of which they are derived) is the only pertinent theory for tackling the problem of the very initial state of the universe. This is however a very cheap escape, for we cannot rely on GRT for the construction of our cosmological theories, and then remind ourselves that this theory might not be the only or the best basis for cosmology, just at the moment we discover that it may lead to metaphysical interpretations we dislike. A more serious objection seems to be that the mathematical results which are so interpreted are, after all, only certain particular cases of singularities, which depend on special mathematical properties of the complicated spacetime manifold which is used for representing a universe satisfying certain cosmological assumptions. In our case, this would amount to recognizing the existence of an absolute zero of time, and this should not be more surprising or "metaphysical" than the discovery of the existence of an absolute zero of temperature. However things are not so simple. First of all because in every mathematical model of a concrete system we are constrained to interpret all the mathematical expressions as expressing properties of that system, so that we cannot dismiss some of them as accidental mathematical by-products aving no concrete significance. (Note, by the way, that the tendency in cosmology is exactly the opposite, that all the possibilities disclosed by the mathematical machinery are exploited when they can serve to give plausibility to some welcome assumption: simply think of antigravity, whose supporters stress that it can be justified in the Grand Unified Theories). Now, if this is how things stand, one must recognize that the existence of an absolute zero of time is categorially different from the existence, say, of an absolute zero temperature, since it poses the problem of an origin, which the instance of temperature does not. On the other hand, if one remains within the framework of GRT, it is obvious that no physical action may be envisaged which could causally produce the universe "before" the absolute zero of time. Does this prevent us from asking whether there might be a cause of the universe? Of course not, provided we do not pretend this cause to be a physical one, i.e. a cause which is expressed through the highly specialized and restricted features of our present physical theories. In that case such a cause would genuinely deserve to be called metaphysical. Physics certainly does not oblige us to admit such a cause, but it is far from preventing us from doing so either. Only if we make of physics a metaphysics (i.e. if we pretend hat physically definable causality is the only causality) can we make this claim. In view of these remarks it seems arbitrary to say that the situation considered here, if correctly appreciated, shows that the universe is itself an uncaused cause or, in traditional terms, a «causa sui», so that «Anyone, who can live with the concept of the Deity as an uncaused cause, can surely live with the Universe itself as the uncaused cause.» In fact we must say that the physical concept of causality does indeed exclude the possibility of an uncaused cause (otherwise every causal explanation would be intrinsically arbitrary, since we might always suggest of any phenomenon that it is simply caused by itself), while admitting that the concept of causality at its highest level of generality (i.e. at a metaphysical level) does not exclude the possibility of an uncaused cause. Now, it is certain that if this concept appears to be logically sound in itself, we cannot refuse to apply it, provided we remain conscious that the way in which it is applied defines its domain of application: this means that if we apply it in cosmology, we are ipso fact making a claim of "metaphysical cosmology". It is true that we can very well live with the idea of the Universe as the uncaused cause, but this simply means (unconsciously) accepting an immanentist, rather than a transcendentist, metaphysics.
Quite analogous reasonings could be provided regarding other ways of "eliminating" the problem of accounting for the initial or boundary conditions, e.g. within quantum gravity: these eliminations are meaningful only to the extent that physics is essentially endowed with the role and power of a metaphysics.
What we have seen in this paper is that, with the development of cosmology, contemporary science has again found many links with philosophy, which seemed to have been discarded for more than a century. In fact, not only was the tenet largely accepted that scientific investigation must carefully avoid philosophical commitments or dependences, but it was also tacitly assumed (as we have seen at the beginning) that the progress of science would gradually make philosophy superfluous. At most it was conceded that philosophy could perform useful work by analyzing science (especially the language and the methodology of science) and by bringing the current world-view up to date by integrating in it the advancements of scientific knowledge. This positivistic outlook is clearly overcome by the most recent trends in science, in the sense that it becomes ever more clear that scientific research incorporates philosophical concepts and principles, and really contributes to refining them and making them fruitful. Cosmology, after all, is not the only example: present investigations on the mind-body problem constitute another interesting field where philosophical conceptualization and scientific theories come into very close contact, a contact whose meaning is not that we finally bring the light of science to illuminate philosophical obscurities, but that we derive from science a great deal of information and knowledge for improving our philosophical understanding of this fundamental issue.
In fact, every time we have been obliged - in our preceding reflections - to recognize that certain cosmological theories or assumptions are not fully justified, or overstep the current standards of physical science, we have never drawn the conclusion that this has condemned cosmology. Rather, we have been led to see that the adoption of such assumptions as peculiar to its way of being scientific, a way which not only implies the "use" of certain general philosophical principles (as is also the case in other sciences), but is further characterized by the adoption of several intellectual attitudes (typical of which is the adoption of the "point of view of the whole") which are among the salient traits of philosophy. All this does not mean (as certain positivistically minded scholars seem to believe) a risk of corrupting the purity of scientific rigour, but a step towards recovering that unity of knowledge which we have lost for too long a time. This unity comes not so much from the use of a unique type of language, of conceptualization, of methodology (the unity of reductionism), but rather from the exploitation of different intellectual approaches in a mutual interrelation and feed-back regarding certain common problems. Now, as we have seen, the universe is hardly conceivable asa scientific "object"; it is also difficult to define it as a precise "concept" (it is rather something like an "idea" in a Kantian sense); but it has certainly posed one of the most challenging intellectual problems for mankind since its origin. Philosophy, mythology, religion, art and science have each tried to tackle this problem, and it would be arbitrary to exclude one or the other of these approaches, since all help us to "understand" the universe. Therefore it is certain that the most promising advances in the intellectual understanding of the universe may come from recognizing it to constitute at the same time both a scientific and a philosophical problem.
9. See H. Bondi, Cosmology, Cambridge Univ. Press, Cambridge 1960.
10. See B. Kanitscheider, «Does Physical Cosmology Transcend the Limits of Naturalistic Reasoning?», in P. Weingartner and G.J.W. Dorn (eds.), Studies on Mario Bunge'sT reatise, Rodopi, Amsterdam-Atlanta 1990, p. 339.
11. It would lead us too far afield to justify this claim here. I allow myself to refer to what I have published on this subject on several occasions. Som titles are given in the references.
12 This is by no means a polemical remark. In fact it fully corresponds to the most widespread way of conceiving of science to say that the scientific approach consists primarily in a certain way of formulating cognitive problems, a way which, according to many scholars, has even had the effect of "eliminating" as pseudo-problems several problems of philosophy. Therefore, it follows that cer tain problems cannot be seriously taken into consideration in science. Now, in the case of cosmology, we find that many problems, which are identical with those of philosophical cosmology, are seriously taken into consideration. Hence, they remain philosophical as problems but, on the other hand, we see finally that this fact cannot "eliminate" them and does not prevent them from also being considered with the aid of science. As a confirmation of this let us simply take a brief quotation from a very "speculative" philosopher, namely Hegel, who gives the following indication of the (philosophical) questions of cosmology in # 35 of his Encyclopedia of the Philosophical Sciences: «The third part [of the traditional metaphysics], i.e. cosmology, was concerned with the world, its contingency, necessity, eternity, limitation in space and time, with the formal laws in its mutation, and finally with the liberty of man and the origin of evil». It is certainly difficult to deny that most of the questions listed above are among those which are deeply debated in contemporary "scientific" cosmology, but this is exactly the reason for recognizing that this cosmology cannot be just scientific.
13. See for example Wheeler 1977, and Vilenkin 1982.
14. See Kanitscheider 1990, pp. 344-345 for this discussion.
15. Let us remark that already at the level of common experience we are familiar with forms of causation that are not "physical" in the sense of not being accounted for by physics. All intentional acts, which are caused by voluntary decisions, are of this kind. The claim that these decisions "in principle" or "in the last analysis" also depend on physical causality is a dogmatic tenet of a bad materialistic metaphysics.
16. See J. D. Barrow, The World within the World, Clarendon Press, Oxford 1988, p.227.
17. See again Kanitscheider 1990, pp. 348-349.
E. Agazzi, A. Cordero (edd.), Philosophy and the Origin and Evolution of the Universe, (1991), (Dordrecht: Kluwer), pp. 27-28, 30-44