On the Nature of Life
What is Life? The Originality, Irreducibility, and Value of Life, 1997
The following questions were posed to me by prominent scientists after I presented the principal contents of the book for the first time as a paper. I will present the objections of my interlocutors here anonymously and in my slightly adapted version of their questions. 
1. On the Significance of Emphasizing the “Many Meanings” of “Life”
Objection: Some scientists will object: It is superfluous to stress that we speak in many senses of “life” or of being. Not only “life” and being are ambiguous notions, but all other words as well. Any word has many meanings.
Answer: While virtually every word and philosophical term has many meanings, many words have multiple meanings only for arbitrary linguistic reasons, which can give rise to equivocal terms. For example, the English word “top” can mean a spinning toy for children and a mountain top, or the German word “Schlob” can mean a lock and a castle. But it is hardly meaningful to say, “Of tops we speak in many senses,” because no inner reason occurs in the object for a manifold meaning of the word. Other terms have only slight differences in meaning, depending on the species to which you apply the same generic term, as when you apply the word “red” to a light red color or to a dark red color, or the word “dog” to poodles and German shepherds. Here, too, we would be pompous in saying, “Of red or of dogs we speak in many senses, sometimes of dark red, at other times of light red, sometimes of poodles, and other times of German shepherds.” Even where the same term expresses radically different meanings, between which only a metaphorical analogy obtains, we do not apply this phrase, as in the case of mathematical triangles and three lovers to which we refer as “triangle.” Where good reasons exist to confound two radically different meanings of the same term, however, it is necessary to distinguish the “many senses” of a term. This is even more important where we find some analogous similarity between two terms. The terms “being” or “life” possess at the same time a profound difference in meaning and involve a deeply meaningful unity and similarity between their distinct referents. This “similarity-in-difference,” a similarity between objects which belong to quite different kinds of being and whose similarity is not based on some common generic feature, was called “analogy” by ancient and medieval philosophy. With respect to these analogous objects and analogous terms, we must take into consideration the whole spectrum of their meaning and become aware how they are used differently. In our context of a discussion of the origin of life, biologists should realize that the organic life that they investigate is not the only kind of life, and, if they could successfully reduce it to material systems (which I deem impossible), they should not therefore consider also other life, for example, that of the mind, equally reducible to matter. Mental life is much more evidently irreducible to matter than the life of bacteria or of viruses. With regard to viruses, we may well have doubts as to whether they actually live or whether their reproduction is something analogously mechanical or purely physical as the “growth of crystals. Most biologists today believe that viruses are not alive, although they do possess genetic information and can multiply in other organisms including bacteria. For outside living cells distinct from themselves, they cannot carry on life processes. Viruses show life processes, and specifically metabolism and reproduction, only when they are in the living cell of a plant, an animal, or in bacteria, in which they are called bacteriophages. Philosophically speaking, one can well ask, however, whether the purely parasitic character of viruses is sufficient to deny life to them if they do show all essential signs of life when they inhabit other cells.
Keeping in mind the radically different forms of life and the analogy between them, the biologist will become more cautious in making claims favoring reductionistic models of explaining life.
2. The Autonomy of Philosophy and that of Science with Respect to Life
Objection: You made intrusions into scientific spheres which I do not completely share. You implied the autonomy of philosophy when you referred to the need for a properly philosophical treatment of the question, “What is life?”. Parallel to this claim, I would hold scientific investigations of life to be completely independent of philosophy. Otherwise if philosophers were in principle to impose limitations on scientific endeavors, we could be faced with a new Galileo case. Philosophers are also autonomous, and they can investigate life independently with their methods. Life lends itself to an exploration from the points of view of many disciplines. Should we then not insist on a complete autonomy and mutual independence of philosophical investigations into life and of scientific biological explanations of life?
Answer: I agree fully with the idea of the autonomy of the methods of science and of philosophy if this “autonomy” means that the disciplines and methods of both are quite different and have different formal objects. Empirical science uses sense perception, observation, experiments, hypotheses, and complex theories, to explore the factual sides of the world. Philosophers look for highly intelligible and necessary essences and essential features of the world open to evident cognitions and insights, as well as to deductive demonstrations. Mathematicians do the same when they really attend to the principles of numbers, geometric objects, and other data, and when they are not only construing ideas, a procedure which plays a legitimate role in mathematics. The reason for a difference in method between science and philosophy or mathematics lies in differences in the formal objects and purposes of the respective methods. For example, intrinsically necessary essences and essentially necessary states of affairs are grounded in aspects of knowledge, in freedom, in conscious acts, in motion, in matter, and in mind. Philosophy should explore these. But contingent facts and essential structures of complexities also exist which only empirical methods can elucidate. Thus, the clue to why we need different methods lies in an understanding of the different kinds of essences and objects. Non-necessary, contingent essences, the elements of which are held together by some factual, non-necessary although quite meaningful bond, do not allow insights into necessary evident truths. Scientists who explore them must use empirical and experimental methods. But to apply these methods to questions of philosophy and mathematics would be absurd. The mathematician would laugh if she or he were asked to conduct years of experiments to know that 2 x 2 can never equal 5. Equally absurd would it be to solve philosophical questions of ethics and oughtness by means of empirical studies of human or animal behavior. Psychology or sociology can investigate empirical questions of human behavior, but philosophy uses quite different methods designed to give us knowledge about the highly intelligible and necessary aspects of reality. 
For philosophers to think that they could interfere in empirical matters would be quite inappropriate. They cannot explore, by means of their methods, the position of the sun or the relationship between the movement of the earth and that of the sun, the empirical marks of life, for example, the different parts of the nutritive or other body systems, the species of insects, or the cellular structure of living organisms and the functions of the parts of cells. They should leave these matters to empirical science to explore. If they do not, a Galileo case may result. Usually, philosophers are less prone to intrude into the sphere of empirical matters than are scientists to speak about philosophical questions. Scientists evidently cannot solve philosophical issues by means of empirical observations; equally evident is that philosophers cannot solve the above-mentioned empirical questions by means of philosophical methods.
Some philosophers, especially those who conducted empirical investigations, like Aristotle, Avicenna, or Albert the Great, exerted a strong influence on science. That influence was inappropriate inasmuch it was based on their general authority in philosophy that was transposed to science, or, because they conflated empirical and philosophical methods. When philosophers try to solve problems of empirical science with their methods, the disastrous result may be a restriction placed upon empirical science that lasts for centuries. Although Aristotle and Albert the Great, in antiquity and in the Middle Ages, conducted empirical science, the Aristotelian idea that all universal natures are necessary has dominated Western thought and impeded for a long time the rise of experimental sciences.
Stanley Jaki, who uses historical, philosophical, and scientific methods and whose education in many disciplines allows him to see their manifold relations, has examined this phenomenon in many perspicacious books. He has shown convincingly many mutual connections between empirical science and philosophical positions. He has demonstrated that only a creationist metaphysics which sees the origin of nature in a free divine act and therefore recognizes contingency in nature, was able in the history of science to provide the proper metaphysical basis for empirical sciences.
This knowledge must not lead us to believe that no absolutely necessary and immutable essences exist which a priori sciences as mathematics or philosophy investigate. We should not believe that in the field of objects of these a priori sciences empirical methods would be justified, so that it would be possible to establish the morally good by statistics or by behavioral studies of animals. A priori is not meant here in the subjectivistic Kantian sense but in the sense of objective essential necessities. I do not deny that philosophy should take its starting point in experience, namely, in a such-being experience in which we come into contact with contingent facts and with essential necessities. I recognize many fruitful mutual relationships between the disciplines and the value of each, but the difference of their methods absolutely forbids philosophers to meddle with the domain of science and to attempt to solve by a priori theories those problems that only empirical science can answer.
But what applies to philosophy, applies more so to science. A disaster occurs if ethologists who observe animal behavior deduce ethical conclusions from this, as do Konrad Lorenz, Wolfgang Wickler, and many others. Scientists frequently trespass over the limits of their discipline. This is legitimate if they have a proper philosophical education and only as long as they realize that they are now speaking as philosophers and not as scientists. For example, Einstein’s theory of the relativity of time has purely scientific aspects resulting in important formulas regarding mass, acceleration, and energy, such as E=mc2. But he also develops philosophical theories about the essence of time and simultaneity being relative, which in no way follow from his physics. The same is true about Heisenberg who deduces from the physical aspects of his discoveries regarding the uncertainty relation, as well as from Einstein’s theory, far-reaching philosophical consequences, which in no way follow from scientific results, regarding indeterminacy, freedom, causality, the first principles of being, and other issues. The same is evident about the theories of evolution and of the Big Bang, which, in most of their forms, are chiefly philosophical theories for which the scientific research provides at best a starting point. This applies still more to the outrageous metaphysical claims about chance, necessity, and God, which Jacques Monod makes in his Chance and Necessity. This becomes the source of many errors as soon as scientists become unaware when they are invoking purely philosophical theories which have nothing to do with their science, and when they hold false philosophical theses as if they were empirically demonstrated.
The mutual autonomy of methods and the danger of intruding into the fields of our colleagues, do not imply a complete divorce between scientific and philosophical methods and investigations. Therefore, I would not agree if you proposed the complete independence of philosophy and science from each other as well as the complete distinctness of methods. We have to recognize the described autonomy and the many mutual relations between philosophy and science. For example, biologists presuppose many philosophical categories, like reality, existence, proof, argument, logical laws, matter, space, time, indeterminacy, determinism, and finality, many aspects and the general essence of which they cannot explore by means of their methods but which are objects of philosophical analysis. The same is true about truth, the scope and purpose of each science, the value and limits of scientific knowledge. All these are philosophical problems. The scientist presupposes implicitly some answers to them which only philosophy can give. Jaki showed convincingly that even a metaphysics and theology of contingency and creation was necessary to make empirical sciences possible and to provide their proper philosophical foundation.
The philosopher also profits from science in many ways. Philosophical questions are posed by science to the philosopher. Scientific experiments and results about the brain can widen the scope of philosophy and corroborate or inspire new philosophical discoveries of “a priori” structures, which I understand as objective essential necessities and intelligible truths. Many of these become accessible only through a special type of experience. But the role which experience plays for philosophy and for biology is totally different. Experiment has no relevance for philosophy except for corroborating or calling into question from the outside the results of philosophy. Thus, philosophers can be pleased when the results of their philosophical studies are corroborated by empirical sciences, and they are forced to check the adequacy of their methods when their results do not harmonize with the results of empirical science. Yet the experiment is never the philosophical method. The philosophical method is another kind of knowledge: insight (intuition) into highly intelligible and evident essences and states of affairs, and deductive demonstrations.
3. Can We Stand Between or Beyond Reductionism and Anti-Reductionism?
Objection: Do you make the tacit assumption that the alternative between reductionism and the recognition of irreducibility, between reductionism and non-reductionism or anti-reductionism, is complete? The main philosophical merit of the issues which we discussed during this dialogue (the emergency-of-complexity-problem, dynamical chaos-theory, non-linear thermodynamics), consists in demonstrating that there is a third possibility. Some new systems and ideas about the origin of life are not physicalistic and materialist in the sense of old reductionism. Can we not stand between or beyond reductionism and anti-reductionism? Life cannot be deduced in a predictable mechanistic manner from physical laws. But life can emerge in unpredictable ways from physical systems, whether these are conceived deterministically or indeterministically.
Answer: Thank you for your interesting objection. I agree with the fact that new forms of theory of matter and of living organisms have emerged, and that these are superior to older ones in that they allow us to account for many more astonishing features of material systems and objects than the older theories had suspected existed. Any theory which opens up to new and verifiable or plausible principles of explanation is less primitively reductionistic than older mechanistic reductionisms which did not include reference to non-mechanical laws like those of teleological (finalistic) principles and purposes, of the “anthropic principle,” of dynamic chaos-theories, and of non linear thermodynamics. Today most scientists will agree that life cannot be reduced to predictable patterns of mechanics, in terms of which Julien Offray de LaMettrie and René Descartes proposed to explain animal and plant behavior. To admit this and to allow for the unpredictable or for purposes which are not reducible to unpredictable chance, as, for example, the anthropic principle in the cosmos, is less reductionistic than theories which did not admit these forms of phenomena and these principles of the emergence of order. Matter has become far more mysterious in the light of modern physics than it appeared before. Explanations of matter which allow for the unpredictable emergence of phenomena are far less reductionistic than purely mechanical models of explanation which admitted nothing but mechanical causality. But do these new theories cease to be reductionistic? Any form of explanation which does not do full justice to the phenomena and essences of things is reductionistic, when it is offered as a sufficient explanation of these data. A good example would be a chess game. Its explanation in terms of a pure theory of wood of which the pieces consist, and of mechanical causality by means of which the pieces are moved by hands or computers, would not explain anything about the essence of chess. This explanation would not explain the moves because it ignores the principles and rules of chess, including the timeless mathematical, logical, and chess-specific principles. It would ignore, among many other aspects of the royal game, the chess-conventions, the intelligible systems of end-games or of openings, and the computer programs based on these. Even to introduce into the theory of chess the occurrence of non-mechanical, unpredictable patterns of behavior not explicable in terms of classical mechanics would be insufficient as explanation. Such an explanation fails to take into consideration the entirely new sphere of rules, geometrical and logical and chess-specific necessities understood by the players, and the sphere of purposive action and intelligent understanding of chess masters.  The most high-level modern physical theory of chess in terms of chaotic and non-chaotic physical systems would be radically reductionistic because it entirely leaves out of consideration the most basic and the more complex principles necessary to explain the moves in a chess game.
To explain life in terms of those same principles which you consider to lead to a theory beyond reductionism would be much more reductionistic than to explain chess games in these terms. For chess does not lie. Therefore, in chess, we can admit such categories as conventional rules and logical and mathematical necessities, and then say that the substantial being (the substance) in which all these programs, etc. are stored, for example, the chess computer, is a purely material thing. The material substratum of chess computers or programs like Mephisto or Chess-Base , or the material thing underlying the actual moves of chess pieces are pieces of wood, plastic, or metal. But this explanation would not be enough for a non-reductionistic explanation of life or of mental life. Life requires entirely new categories to be understood properly, transcending all those required for explaining a chess game. Life requires new substantial categories, as, for example, entelechies, life-principles, souls, and minds. I do not deny that the properly human personal acts of understanding chess games, or of inventing them, require minds and can never be performed by chess computers which understand absolutely nothing of the game though on a basis of purely material causes which are correlated to mental acts in computer programs they simulate a brilliant understanding of chess. I argued in my book on chess philosophy that any understanding and human playing of chess presupposes minds. Nor do I deny that the invention of chess-computers is a specifically human act. But given the existence of a chess-computer, the explanation of the moves it makes does not require any spiritual substance or mind. Yet we cannot understand its moves or the program it uses and the causes which made it, if we do not understand many conventional and a priori rules and principles which go beyond those which dominate physical systems.
We must not only ask: Is modern life-theory in science less reductionistic than classical mechanical models of materialistic life-theories? But: Is it sufficiently non-reductionistic? Do the principles modern physics introduces for the explanation of life, for example, in terms of modern chaos-theory, do justice to life? I would answer: even incomparable less than if these theories were applied to the explanation of chess games. Heisenberg, as expressed in his book Physics and Philosophy, could discover analogies between his interpretation of the uncertainty relation, in terms of the alleged indeterminacy of quantum-physical micro-processes, and freedom. This is fascinating, although Heisenberg’s philosophical interpretation of his ingenious discoveries in physics involves a confusion between freedom and chance and a conflation of epistemology and metaphysics. Our inability to measure with precision both the speed and location of particles and our resulting ignorance about certain aspects of physical properties and causes of micro-physical events is confounded with the alleged metaphysical absence of any determining cause of material events and their alleged ontological indeterminacy or uncausedness. Matter and material events, I submit, necessarily require an efficient cause through the power of which they are or happen, whether the efficient cause of material events is immanent in nature or transcendent to it, as in the case of free actions upon matter. Inanimate matter cannot be free or act from an inner principle of spontaneous motion. Absolute chance is not possible or a viable substitute of a causal principle of explanation. Therefore, matter is necessarily determined, but in the last analysis, determined by freedom.
In these and similar ways, in spite of the astonishing advances of modern scientific explanations of matter in comparison with older ones, modern theories of life and consciousness in terms of material evolution are just as reductionistic as the older ones. Only the nature of a given object can tell us whether it is an ultimate irreducible datum or explicable in terms of something else. Only the intelligible natures of things themselves dictate whether more sophisticated materialist explanations of life are reductionistic. If life requires an entelechy or soul, as Aristotle says, and as I have argued in this book and in other works, then even the most sophisticated materialist models of explaining life, using non-linear equations, chaos-theory, or quantum physics, remain reductionistic and inadequate when they seek to reduce life and consciousness to “nothing but strikingly new phenomena of the physical universe.” Basically, these models are then just as reductionistic as the old reductionisms which sought to reduce life and mind to the level of pure machines and to other phenomena known to physics at that time. Life, especially mental life, just cannot be thus reduced. If unpredictable laws or events in the material world are equally unable to explain life or even a chess game as predictable ones, a theory of life or chess in terms of them remains reductionistic. Modern chaos-theoretical explanations of life introduce unexpected laws that explain unexpected events in the physical universe. But if these laws are quantum-mechanically conceived, deterministically or not, and interpreted in terms of chance-events, none of this can change the fundamentally reductionistic character of these theories. De LaMettrie’s theory of mind, expounded chiefly in his L’Homme machine, 1747, might have been much more primitively reductionistic than these modern theories, but an interpretation of minds in terms of more complex material systems remains equally reductionistic. The matter at hand is this: Can biological life and mental life – can bios or zoee – be reduced to complex brain-events, brain-processes, cells, modules, and the electrical and chemical occurrences in the? If not, any attempt to explain them in these terms remains reductionistic and different only in degree from older forms of reductionism.
4. The Question of Life as a “Transdisciplinary” Question
Question: You call the question of life an “interdisciplinary” question, and I am inclined to agree with you. But would we not better introduce the term “transdisciplinary” to indicate the need for a closer cooperation among the disciplines and to avoid a situation in which “interdisciplinary studies” only mean that many disciplines examine the same object from the narrow point of view of their own method? Your use of the term “interdisciplinary” goes against what you have said. Life or death are “transdisciplinary” objects. To explore topics such as life or death requires that one and the same investigation use many methods.
Answer: I agree with your viewpoint in that we would be quite wrong to conceive of “interdisciplinary” studies thus that each member of a discipline studies an issue of “material” objects as, for example, death only from the discipline’s point of view and with its methods, without taking into account the results and methods of other disciplines. The term “material object” is not taken from matter but constitutes the opposite of “formal”. Interdisciplinary studies would not mean a sum-total of studies which remain each enclosed in only one discipline. Instead, the goal of interdisciplinary studies is to arrive at a more comprehensive understanding of the Issues at stake, b leaving the narrowness of your own discipline. In this respect, we can legitimately speak of transdisciplinary studies rather than of interdisciplinary ones, although the term “transdisciplinary” and “interdisciplinary” stand in need of explanation.
“Transdisciplinary studies” would be most undesirable if “transdisciplinary” meant that we non longer respect the different methods of different disciplines, or that scientists do amateur philosophy and wrong philosophy which they pass for “scientific” or “transdisciplinary”, or that philosophers engage themselves in amateur scientific theories. We should approach an issue by the methods which are appropriate to it and which pertain to a discipline which we master and whose methods we use conscientiously and rigorously, without attempting an amateurish crossing of the borders. Interdisciplinary or transdisciplinary studies should not mean, for example, that scientists get involved in forms of unfounded opinion as does Jacques Monod, who in his Chance and Necessity philosophizes in the most hair-raisingly amateurish way, talking about the highest matters of metaphysics. The sophisticated and adequate scientific knowledge on which Monod’s success in micro-biology and other sciences depended did not prepare him in the least for philosophical theories. “Transdisciplinary” cannot mean a “nihil obstat” to incredibly naïve pseudo-philosophies of scientists or to similarly naïve scientific theories of philosophers. In a properly interdisciplinary or transdisciplinary study, we should check with a representative of another discipline whether we interpret its results correctly, and we should never falsely claim authority in fields and methods outside the scope of our competence. If we are unprepared to pursue philosophical investigations, we should leave those to the philosopher and not engage in audacious philosophical theories without the necessary rigor of properly philosophical methods.
The greater danger is for scientists to think they know philosophy than for philosophers to think they know science. While philosophy does not turn a philosopher into a scientist, many people think that anyone is prepared to philosophize. This is true in that every woman and man has some philosophical assumptions and can in principle know philosophical truths. But the proper exposition and understanding of philosophical truth is not an easy task and it requires deep reflection and proper training, as well as philosophical talent and a fundamental attitude of openness toward being. The illusion whereby all people who know something else easily come to think that they are also good people who know something else easily come to think that they are also good philosopher, is basically the problem of doxa described by Socrates in the Apology. Whereas Socrates, the philosopher, knows quite well that he does not understand the several crafts, poetry, and the intricacies of political life, the craftsmen and craftswomen, the poets, and the politicians think they know all philosophy. Socrates knows his limits, whereas the representatives of other fields think that, because they know some things which the philosopher does not understand, they know all others and the most important objects of philosophy as well, even if Socrates can easily show that they know nothing about them. This does not exclude that some individual scientists were also great philosophers and that many scientists who have not been great philosophers nevertheless gained many philosophical insights, as I tried to show elsewhere of Sir John Eccles with respect to the “self-conscious mind” .
5. Mental Life Cannot Be Identified with the Brain
Objection: You presented a critique of reducing thought and will to the individual brain, to which indeed they cannot be reduced. But deducing from this that mental life cannot be reduced at all to brains is to take too big of a step. The irreducibility of thought to individual brains and brain-events does not yet prove that mental phenomena are irreducible to a community of evolving brains which develop in a cultural environment which programs these brains. We can note the tremendous influence of learning on brains, and isolated brains would never develop in these ways, even in purely physiological terms. Our brains would never have developed many of their functions if they had been left in an isolated state. We need a new phenomenological method to explore emergent aspects of brains, as members of a society of brains. Therefore, how can your objections refer to an emergent community of brains? Why could we not say instead that the individual brain in its uninfluenced state is insufficient to explain thought? But the brain which has been subjected to a process of brain-programming can explain thought, social life, language and all other human activities. The mere physical organ of the brain, the consequence of the genetic code and of a hardware-program can none of them explain the mind. An explanation is however provided by the multiple effects of the “software-program” which comes to our brain from the world, from the objects of perception, experience, and memory, and even more from the interactions of our brain with other brains in schooling, learning of any kind from others.
Answer: I fully agree with you on the idea that the “programming” of the brain as well as the complex spatiotemporal patterns in the modules of the brain occur by the immanent individual structures of the brain yet include manifold changes of brain-activity and of something like “brain-programs,” changes which are consequences of experience and of manifold external influences. Memory in all its forms gives a splendid example of this, but so does any form of learning or understanding.
Analogous to the above remarks about the more subtle reductionisms of life to phenomena explored by quantum-physics and chaos-theory, reductionism still occurs in reducing mental life to the sum-total of complex brain-events. Whether you have many brains or one, brains which function according to teleologically conceived patterns of modular programs or according to primitive chance and necessity, explanations of mental life in terms of distinct principles of explanation are only different degrees, although perhaps essentially different degrees, of reductionism. None of this influences the central philosophical question: “Whether any conceivable material substance which can store programs, with its billions of brain cells, can be the substantial subject or substratum evidently required for thought? If my arguments against this are valid, your theory remains essentially reductionistic. We cannot possibly assume that the subject of thought and will, which can be shown to be an indivisible, simple, and spiritual substance, the personal self, could be identified with a brain subjected to manifold external influences from the world and from other brains, or to a plurality of brains. If it is essentially and necessarily impossible, as I tried to show, that the personal self be identical with one brain or with a part of a brain which, in its physical complexity of cells and of parts thereof, is utterly incapable of producing even the tiniest thought or conscious act, then it is equally impossible that the mind be reduced to one brain modified by other brains.
Programs or spatio-temporal patterns of brain-activity influenced by them, are less capable of being the ontological subjects of intellectual or free acts than a brain. They are not substantial entities like persons. The fundamental brain-physiological reductionism does not cease to be reductionistic if we add to our brain other brains and their interaction with our brain events. In the final analysis, none of the phenomena discussed in this book in the context of the proofs for a spiritual soul are more explainable in terms of many brains than in terms of one brain, or in terms of a brain programmed by external influences as opposed to an isolated brain. I have tried to show this in several books and articles on the body-soul problem. Consciousness cannot be an emergent or a supervenient property of a brain or of a “society of brains,” just as little as conscious life can be an epiphenomenon of a single brain.
 The original version of my paper, «The Irreducibility of Life to Chaotic and Non-Chaotic Physical Systems,» and the discussion – with the names of the scientists – will be published by the Pontifical Academy of the Sciences in the Proceedings of a Meeting dedicated to Life and Chaos Theory.
 See Dietrich von Hildebrand, What is Philosophy? (Milwaukee: Bruce, 1960; 2nd ed. Chicago: Franciscan Herald Press, 1973; 3rd ed., with a new introductory essay by Josef Seifert, London and New York: Routledge, 1991), 7, pp. xii ff., and ch. 4; see also Balduin Schwarz, “Dietrich von Hildebrands Lehre von der Soseinserfahrung in ihren philosophiegeschichtlichen Zusammenhäengen,” Wahrheit, Wert und Sein: Festgabe füer Dietrich von Hildebrand zum 80. Geburtstag, ed. Balduin Schwarz (Regensburg: Habbel, 1970), pp. 33-51; and Josef Seifert, Back to Things in Themselves: A Phenomenological Foundation for Classical Realism (London: Routledge, 1987).
 Josef Seifert, Das Seib-Seele Problem und die gegenwäertige philosophische Diskussion: eine kritisch-systematische Analysie (Darmstadt: Wissenschaftliche Buchgesellschaft, 2nd ed. 1989).
 See Josef Seifert, Schachphilosophie (Darmstadt: Wissenschaftliche Buchgesellschaft, 1989), ch. 2 ff.
 In Seifert, Das Leib-Seele Problem (soon to be published in English).
J. Seifert, What is Life? The Originality, Irreducibility, and Value of Lfe (Amsterdam: Rodopi, 1997), pp. 111-122.