INTRODUCTION

To offer the twentieth-century reader an English version of a Latin commentary on a treatise written in Greek during the fourth century before Christ is an act which demands some explanation. This Introduction is intended to satisfy, at least in part, that demand.

I. ARISTOTLE'S PHYSICS

The Original Treatise

From B.C. 335 to 323, Aristotle conducted his school of philosophy and science in Athens. One of his regular courses dealt with the nature of the physical world, the cosmos. This was the same subject which had engrossed the first philosophers of Greece, from Thales to the Timaeus of Plato. Doubtless Aristotle's lecture notes grew through the years, incorporating more and more of his meditations on phusis (reality as subject to change), on kinesis (motion itself), and on the ultimate origins of motion in the universe. Certain specialized Aristotelian treatises (On the Heavens, On Generation and Corruption, and Meteorology) are related to this course but the chief record that we now have is the work called the Physics, in eight books.

             After Aristotle's death (B.C. 323), Theophrastus became head of the Peripatetic school. It is possible that he introduced some changes into the works of Aristotle. There is much debate as to what happened to the master copies during the next two centuries. Some manuscripts which had been in Theophrastus' possession were removed from Athens by Neleus. In the first century before Christ, Andronicus (and possibly other editors) gathered the works of Aristotle and arranged them in the form in which they are now extant. The course on Physics was followed in this classical edition by an assembly of treatises on being-in-general (which latter was then entitled, ta meta ta phusika, giving rise to the word, 'metaphysics', which simply means what follows the Physics). Modern Aristotelian scholars (W. Jaeger, J. Owens) have come to the conclusion that the Metaphysics is a collection of treatises and notes, arranged by later editors from disparate materials written at different periods by Aristotle. Some (notably J. Zürcher) have suggested that most of the Aristotelian corpus was actually written by Theophrastus--but this view has found little favour. In any case, the eight books of the Physics seem to have more unity than the Metaphysics and, while the text may have suffered some early editorial modification, present-day experts regard the Physics as a rather accurate record of what Aristotle actually taught.

Mediaeval Latin Versions

No Latin translations of Aristotle's Physics are known to have been in existence before the twelfth century A.D. With the exception of certain logical treatises, none of the writings of Aristotle were put into Latin in the early Christian centuries. The twelfth and thirteenth centuries witnessed many attempts to remedy this situation.

             We can identify five Latin versions or revisions of Aristotle's Physics preceding Thomas Aquinas' Exposition: (1) an Arabic to Latin translation, attributed to Gerard of Cremona, made at Toledo before 1150 (of which there is now a manuscript in the Library of the Seminary at Aosta); (2) a Greek to Latin version of the first two books, dating from about 1150 (now preserved in Cod. Vat. Regin. 1855); (3) another Arabic to Latin version of the complete Physics, mentioned about 1170 by the medical doctors, Ursus di Lodi and Maurus of Salerno; (4) an early thirteenth-century Arabic to Latin text with the Commentary by Averroes, translated by Michael Scottus before 1235; and (5) the Moerbekana, a revision by William of Moerbeke of the first Greek-Latin version and produced during the lifetime of St. Thomas.

Text used by St. Thomas

When the first Renaissance printers published Aquinas' commentaries on Aristotle, they found that the mediaeval manuscripts lacked a Latin text of Aristotle. The custom was to copy only the first few words (cue-words) of each section of Aristotle as an identification of the entire text under discussion. The usual practice of the manuscripts may be observed in our printed editions of Roger Bacon's commentaries. As a consequence, these printers obtained a Latin version of Aristotle, made by a humanist scholar, and printed it with the commentary by Aquinas. Some modification was made in order to avoid a too apparent discordance from the cue-words in the exposition. In some printings, two texts of Aristotle are given: the Recens is the humanist version and the Antiqua is a mediaeval translation. Modern printings of Aquinas' commentary on the Physics simply reproduce the Renaissance texts of Aristotle; this is true even of the famous editio Leonina. This means that our Latin texts of Aristotle, as now printed with the commentaries by St. Thomas, are neither the version of William of Moerbeke nor are they the precise mediaeval translations read by Aquinas.

             It has been assumed by many scholars (influenced by the account in the early Latin Lives of St. Thomas) that Moerbeke supplied Thomas with reliable translations which were used throughout his expositions of Aristotle. There is now some doubt as to the validity of this assumption. In commenting the Physics, St. Thomas may not have begun to use the Moerbekana until about Lectio 2 of Book II. Throughout the exposition of the first Book, Aquinas appears to be reading a pre-Moerbeke version similar to that of Cod. Urb. 206, of the Vatican Library. After starting the second Book, he seems to have shifted to the Moerbeke version, a text similar to the Physica Nova (Vat. Lat. 2083). As a matter of fact, the actual manuscripts used by Thomas probably contained a mixture of various translations (what the German scholars call a Kontamination) deriving from the efforts of mediaeval copyists to produce a readable text from the several versions available to them. In the expert judgment of Canon Mansion, the printed text of Aristotle's Physics which most closely approximates the Moerbeke version is one found in an early edition of Giles of Rome.

             From the foregoing it becomes apparent that, in the present state of scholarship, one cannot precisely identify the Latin manuscripts of the Physics which Thomas Aquinas used for his commentary. It is, then, not feasible to attempt an English translation of the Physics, in the text (s) which Aquinas read. However, it is clear from the Expositio that Thomas had a text which was not much different from our present Greek editions. Except for Book VII, Chapters 2-3, one usually has no difficulty in locating the pertinent passages in the Oxford English translation done under the editorship of Sir David Ross. The correspondence between this English version and St. Thomas' commentary is often remarkably clear and always sufficient to justify the translators of the present volume in recommending that its readers consult the Oxford translation of the Physics, in the course of their reading.

II. AQUINAS' EXPOSITION

In spite of obvious differences between the thought of an ancient pagan philosopher and a Christian theologian of the late middle ages, it is generally admitted that Thomas Aquinas produced one of the best commentaries on Aristotle's Physics. The present work, then, is an excellent explanation of the original work of Aristotle. More than that, it is a clear presentation of the sort of cosmology from which men like Copernicus, Galileo, Kepler, and even Newton took their start in founding modern astronomy and physics.

Occasion and Date of the Commentary

Thomas Aquinas took his degree in theology at the University of Paris in 1256, taught there for three years, and then spent a decade on various assignments in the Dominican houses of study in central Italy. Aristotle's works on natural philosophy had been subject to various ecclesiastical censures at Paris from 1210 to about 1245--in the sense that lecturing on them was forbidden though private study of them was not. Of course, Thomas had encountered some Aristotelian philosophy in his studies of the liberal arts at the University of Naples, in the classes of Albert the Great at Cologne, and through his reading in the works of other philosophers, notably Avicenna. In 1259 (June) a group of Dominican scholars met at Valenciennes and recommended a new programme of studies for the training of members of the Order of Preachers. In this programme, some work in the liberal arts (and so in philosophy) was prescribed for the young men in the Order--apparently with the strong support of both Albert and Thomas. Since Aristotle was by now recognized as the great philosopher, it is obvious that good Latin texts of his major writings had to be obtained and the manner in which a Christian school might use these treatises had to be determined. St. Thomas went on to Italy and in 1262, during the Pontificate of Urban IV (a Pope interested in philosophical learning), was in residence at Orvieto, where the papal court was then situated. Albert the Great was also at Orvieto in that year. Still more significant, a Dominican missionary with a good working knowledge of Greek had been recalled from the East and stationed at Orvieto. He was William of Moerbeke, a man who had already translated in 1260 at Nicea the Greek Commentary by Alexander of Aphrodisias on Aristotle's Meteorologica.

             This was quite an assembly of talent at one Dominican house of studies. Though contemporary records are curiously reticent on the matter, it seems that in these years which Thomas spent in Italy (before returning to the University of Paris in 1269) he was the centre of an organized effort to make Aristotle available to the world of western scholarship. In any case, it is historically certain that William of Moerbeke now spent many years (1262 to about 1278) on translations of the works of Aristotle and his Greek commentators. Thomas Aquinas was using the Moerbeke texts, during these same years, for at least some of his commentaries on Aristotle.

             It is reasonable to conclude that Aquinas prepared his Expositio in VIII libros Physicorum Aristotelis during the 1260's. No dated manuscript of his commentary has been found; nor do the early Lives of St. Thomas, or other contemporary documents, provide a precise date for the Exposition. The contention that St. Thomas used a pre-Moerbeke text of the Physics for the first book of his exposition does not pinpoint the date, for we do not know when William began to translate the work. Canon Mansion made a comparison of Thomas' treatment of time (In IV Phys., Lect. 23) with Albert's paraphrase of the same section of the Physics and found that Thomas repeated, 'globally and with close approximation even to details', the interpretation given by his old teacher, Albert. This means that Thomas' comment post-dates 1257. Indeed, Mansion came to the conclusion that the terminus post quem of Thomas' work is 1268. Another study of the chronology of the commentary argues that it precedes the Summa Theologiae, I, the De Potentia and the Exposition of the Metaphysics. However, such arguments from doctrinal content are difficult to control and not too reliable for chronological purposes. On the matter of the eternity of the world, for instance, the doctrine of the commentary on the Physics is considered by Grabmann to be different from what we find in the Prima Pars (1, 46, 1) and De Potentia (III, 17) and quite like the Commentary on the Physics written by Siger of Brabant in 1268. It has been noted recently that Thomas' commentary on the Posterior Analytics (I, Lect. 41, n. 16) refers to the second Book of the Physics. But the example which Thomas cites is not found in Aristotle's Physics; it is in Thomas' own Exposition. This citation indicates a priority of the commentary on the Physics but also, possibly, that they are of much the same time. These various data point to the years, 1268-1271, as the period in which Thomas commented the Physics. Indeed it is unlikely that he worked on the Physics during his second Paris professorate (1269-1271). He was then teaching theology; this was one of the busiest periods in his life; he would then be far removed from Moerbeke, whom he seems to have been consulting while doing the commentary. It is probable that the Exposition was finished in Italy before Thomas departed for Paris in 1269.

             There is still some question as to whether the Exposition, as we have it, is the actual report of oral lectures or a written commentary not stemming directly from the classroom. It can hardly be denied that some of Aquinas' commentaries on Aristotle were orally delivered. There is unmistakable evidence that Thomas actually lectured on the first Book De Anima. Our present text of this is a reportatio, so he must have been giving an oral commentary. Since the general style of these two commentaries is the same, one may conclude with some probability that the Expositio on the Physics was originally a lecture course for the Dominican students at some house of studies in the Roman province. Quite possibly St. Thomas revised it before having copies made of it. This makes dating still more inexact but for all practical purposes we may put the commentary on the Physics in the years 1268-1269.

Style of the Exposition

In general, mediaeval Latin commentators on Aristotle used one of three styles: (1) paraphrase: a loose and sometimes rather personal restatement of the content of a work, without much attention to verbal details of the text (illustrated in the work of Avicenna and Albert); (2) questions: a series of problems suggested by the text but not following the original text in all details (exemplified by Roger Bacon's Quaestiones on the Physics); and (3) literal commentaries: expositions of the original, phrase by phrase (illustrated by some of the commentaries of Averroes). It is in the third genre that St. Thomas' exposition of the Physics belongs.

             Aquinas presumes that the reader will be able to consult the text of Aristotle's Physics. Probably he read aloud a section of this text in class (the lectio). Such sections vary in length, do not correspond to chapter divisions, usually approximate what could be put on one page of a modern printed book. The actual comment in each lectio usually starts with a sentence making the transition from the preceding lectio. Then Thomas proceeds to the divisio textus: an analysis of the argument of Aristotle into its main parts, with cue-words used to indicate the divisions. After this comes the expositio textus, beginning with the words: 'Dicit ergo primo', or 'Circa primum sciendum est', or some such phrase. In this exposition, an explanation is offered for each step or point in the reasoning of Aristotle; the cue-words of the divisio textus are repeated so that the reader may follow each part of the argument. Examples may be added or expanded, citations made from other works of Aristotle or his commentators, and on rare occasions Thomas will criticize Aristotle, or more frequently his commentators, for running counter to the Christian faith or for mistakes in reasoning. This usually completes the lectio, though in some cases Thomas adds something by way of conclusion or general summary.

Thomas' Attitude toward Aristotle

While St. Thomas devoted his mature life to the teaching of theology, it is clear that he made a profound study of the philosophy of Aristotle and his earlier commentators, Greek, Arabian and Latin. Aristotle's works and theories are cited as frequently in the theological writings of Aquinas as are those of the best known Christian thinker, St. Augustine. In his various expositions of the actual text of Aristotle, Thomas' primary purpose was to present the meaning of the original author and to explain it for his listeners and readers. Thomas does not forget that he is a teacher in a Christian school (so he will, on occasion, point to some discrepancy between an Aristotelian view and Christian belief) but he makes a very objective and faithful effort to interpret what Aristotle wrote. There is little intrusion of religious bias in Thomas' commentaries and there is much evidence of respect for the mind of Aristotle.

             Aquinas had well developed philosophical views of his own. Here he owed much to Aristotle but not everything. There are other sources of St. Thomas' personal philosophy: Platonism and Neo-Platonism, Stoicism, Boethianism, Christian Platonism (Augustine and Dionysius), Avicennism, Averroism, and the Jewish scholasticisms of Maimonides and Avicebron. That these influences and his personal predilections may colour the Thomistic commentary, it would be idle to deny. No commentator comes to his text with a blank mind. Aquinas reads Aristotle with the benevolent interest of a well-instructed and thoughtful Christian--which Aristotle was not. Yet, when all this has been admitted, we must recognize Aquinas as an expositor who strove to be objective, scholarly, and as historically accurate as the circumstances permitted.

             Lacking the knowledge of Greek to use the original text, Thomas is still critical in his awareness of textual problems. An instance of this attitude is found in lectio 10, of the commentary on Book V of the Physics. There is here a passage dealing with 'violent' motion which Thomas suspects as non-authentic. He reports that, according to Averroes, this passage (231 a 5-20) is lacking in some Arabic MSS., and he adds that it is said to be missing in the Greek copies. He even surmises that it may be an addition from Theophrastus, or some other commentator. Whether Thomas is right or wrong regarding the authenticity of this passage deserves further study; it is a good illustration of his concern for textual authenticity and it shows that he sought information, indirectly, on the Greek text.

             No doubt Aquinas would be surprised at the critical findings of modern students of Aristotle's text. Unlike Werner Jaeger, Thomas considered that the major works of Aristotle are well-organized, complete and unified works. He assumed that we have them in practically the same condition in which they were written. In fact, we have in the present work an instance of Thomas' express resentment of a suggestion by Averroes that Aristotle had been a bit confused about what he is demonstrating at the beginning of the eighth book. Rather sharply, St. Thomas says that it is ridiculous to claim that Aristotle repeated his whole treatment because he had earlier omitted something. He adds that there must have been plenty of opportunity for Aristotle to correct his book and to supply what might have been lacking in its proper place. That Aristotle would have left the text in disorder, is unthinkable to Aquinas.

             On the other hand, St. Thomas never regards Aristotle as an authority on matters of faith. Thus, in the section of the Physics that has just been mentioned, Aristotle argued that the world is eternal. Thomas carefully explains the Aristotelian argument and adds this: 'One part of his position, namely, that there was always motion, conflicts with our faith. For according to our faith nothing has always existed except God alone, Who is altogether immobile.' Then Thomas discusses a second way of understanding this text on eternal motion: some Christian interpreters had suggested the possibility of taking immaterial action as motion, and thus arguing that God's action is what is eternal. This would obviate the contradiction between Aristotle and Christian teaching. However, Aquinas does not take this easy way out; he correctly judges that it relies on an equivocal use of motion and he rejects the suggestion.

             St. Thomas may have read Aristotle with the mind of a Christian but he never thought that he was required to make Aristotle speak like a Christian. Some of his contemporaries tried to prove such a 'concordism' between Aristotelianism and Catholic beliefs but Aquinas did not consciously share this attitude. His view is bluntly expressed in another short work where there is some question as to Aristotle's teaching on the origin of the rational soul in man. Thomas rather abruptly dismisses the question, saying: 'I don't see what one's interpretation of the text of Aristotle has to do with the teaching of the faith. Plainly, Aquinas thought that a scholarly commentary on Aristotle was a job by itself, not to be confused with apologetics or theology.

III. MEDIAEVAL PHYSICS AND MODERN SCIENCE

Reality as Subject to Motion

From Aristotle and Eudoxus the middle ages inherited a picture of the structure and workings of the physical universe. The earth was thought to be a sphere (not 'flat' as the legends about the predecessors of Columbus would have us think) situated at the centre of about fifty concentric and progressively larger spheres. The outermost sphere was pictured as an absolute boundary; beyond it there was no space. These spheres about the earth were thought to be constituted of translucent matter and some of the spheres had smaller opaque bodies imbedded in them. These bodies were the planets. In a static view, one might compare the system to the layers of an onion enclosing the earth as their core, with eight or so pieces of buckshot stuck in different layers. However, the system was not static. The spheres were in motion, rotating in various directions and thus causing the motions of the planets. The earth was considered to be at rest in the centre. This is the astronomy of Aristotle's De Caelo; it is pre-supposed in the Physics and is part of the contemporary science of Thomas Aquinas' century. Though an incorrect astronomy, the geocentric hypothesis was an important step in man's effort to understand his environment. After Einstein, we know that it is nonsense to ask whether the earth is 'really' in motion or at rest; it is mathematically simpler to postulate that the sun is at rest and that the other celestial bodies are moving in relation to it. Even today, ordinary mortals (and weather bureaux) retain the conviction that the sun rises and sets round a stationary earth.

             Another long-lasting and thoroughly erroneous hypothesis in the development of physical science was the four-element theory. Long before Socrates, Greek thinkers assumed that all material things were constituted of earth, air, fire and water. These four were considered simple substances and all other bodies mixtures of these. For more than two thousand years learned men accepted this theory, even when they developed other principles of material analysis. Matter and form, atoms and empty space, substances and accidents--all were accommodated to the four-element theory. It was even extended to the life sciences, giving rise to the physiology of four humours and its consequent applications in medical and nursing practice. Some treatments of colds and fevers, today, are not entirely independent of this old theory. In psychology, the theory suggested the notion of four basic temperaments, of which some vestiges remain in contemporary literature. Indeed the four-element hypothesis (which is very central to the Physics and to St. Thomas' comment) has had a most distinguished and successful career. Of course it was wrong but, like many other errors, it had an important influence on the history of man.

             Because the geocentric astronomy and the primitive chemistry of Aristotle's Physics were erroneous, we should not jump to the conclusion that the whole ancient explanation of nature was therefore wrong. The hylomorphic theory, for instance, is still used in many philosophies of nature. That bodies and their changes are explainable in terms of material and formal components continues to be a basic assumption of much philosophic and scientific thinking. Under other names and with important modifications, this Aristotelian theory partly survives; potency and act, the polarity principle, even particles and structure owe something to it.

             Nor can the notion of four kinds of cause be dismissed as completely irrelevant. These Aristotelian principles of explanation provide four different answers to the question: Why is this thing existing, or this event occurring? Thus, to explain an automobile we might describe the stuff of which it has been made (material cause), the structural arrangement and working design (formal cause), the productive sources of the machine (efficient cause), and the purpose for which it may be used (final cause). Such a fourfold causal explanation can provide a very complete answer to many queries about nature. It should be obvious that 'cause' is used in a broad sense in Aristotelico-Thomistic philosophy.

             Similarly, the analysis of physical things in terms of substances and their accidental modifications is not entirely archaic. In English, the meaning of substance was changed. With John Locke, it came to mean little more than an inert substratum to which accidents are externally attached. Further ambiguity has developed as a result of the special use of 'substance' as a chemical term. In Aristotle and St. Thomas, substance designates any being which exists by itself, as contrasted to an accident which exists in another being.

             Other Aristotelian definitions, concepts and theories will be found in the Physics--notions which have been incorporated into the language and culture of western man. For those who wish a more thorough analysis there is available a book which covers these themes in full detail.

Aquinas' View of Physical Science

The middle ages stressed the substantial and qualitative aspects of the physical universe while modern science is more interested in quantitative and constructural interpretations. For Aristotle and Thomas Aquinas, science is a mental skill in reasoning from premises grounded in sense experience and in intellectual understanding of the universal meanings implicit in that experience. Whatever modern science is, it is not identical with that sort of demonstrative knowledge.

             In the century of St. Thomas, there was a growing school of empirical scientists (Witelo, Albert the Great, Roger Bacon and Robert Grosseteste). They anticipated some of the methods of research and interpretation that are still used in modern physics. But Aquinas had little to do with this experimental movement. He did not emphasize the controlled observation of natural phenomena, let alone the making of technical experiments in the modern laboratory sense. Nor did he fully see the use to which mathematics might be put for the interpretation of empirical data. In all this he is less 'modern' than some of his contemporaries, particularly those at Oxford.

             Thomas Aquinas' notion of a science of nature owes a good deal to Aristotle's Posterior Analytics. He is in full agreement with the view that man has no knowledge, on earth, which does not originate in sense experience. In this, St. Thomas is fundamentally an empiricist, completely rejecting innate knowledge and the sort of thing which will later be called a priori forms of understanding. He adopts Aristotle's suggestion that the manifold of sense experience (empeiria) suggests certain universal judgments to the human understanding. These first items of intellectual knowledge (principles of understanding, such as that of non-contradiction or some of Euclid's axioms) then function as self-evident premises for further demonstrative reasoning. The origin of these intellectual principles is inductive on the level of sensory presentation but the consequent movement of human reasoning is viewed as deductive. His view of discursive reasoning is akin to the procedures of geometry. However, Thomistic science is not purely deductive: even after the initial induction of premises there is a constant effort to refer to additional information coming through further sense experience. This dependence on the 'phantasms' is especially distinctive of the science of nature.

             The last few centuries have witnessed the development of a large number of distinct, natural sciences which treat various limited aspects of physical reality. The techniques of experimental and mathematical physics, of the different types of chemistry, of geology, astronomy, meteorology, and of the many life sciences, have become tremendously diversified. Specialization has pluralized the natural sciences to such an extent that no modern man would pretend to competence in all. Yet there have also been efforts at unification, at a reduction of this plurality to a unified and most general theory of scientific knowledge. Recent developments in nuclear physics seem to make the distinction between physics and chemistry less marked than it was a decade ago. If a unified theory is ever achieved, it will not result from a contraction of knowledge but from a more profound insight into the available data.

             Now the emphasis of St. Thomas' philosophy of nature is on a unified science of physical reality. Of course it was easier in the thirteenth century to be optimistic about such a possibility. This does not mean that there was complete ignorance of the diversity of scientific techniques. Encyclopedic writings of the middle ages describe long lists of mechanical arts in which men had acquired some competence. Indeed, to take but one example, it is obvious that the men who built the cathedrals of Europe were not ignorant in mechanics and the architectural arts. Yet these disciplines were then regarded as manual crafts and their practitioners as artisans. Little attention was paid them in academic circles; there were no trade-school courses in the mediaeval university. Today, we must admit that much of what is called physical science is simply technology. Courses in physics and chemistry consist very largely in repeating the same experiments that have become standard textbook procedures. Actually it is difficult to determine how much technological skill a great scientist must have; some of our best have had but little; St. Thomas had none. If modern science has exalted technics, the mediaeval period exalted thinking. This is one of the major differences.

             Thomas Aquinas was also a metaphysician: he had a well-developed theory of the general character of reality as a whole. With Aristotle he agreed that there are immaterial substances in existence and he sought the ultimate explanation of the workings of the physical universe in the capacity of immaterial being to originate motion in bodies, without being moved in itself. In this the cosmology of Aquinas is ordered to his metaphysics. Modern physics is not so orientated. Causality today means efficiency. The theme of final causality, so important to Aristotle and Thomas, has almost vanished from physical science. With it has gone the notion of teleological order in the universe. It is noteworthy that the life sciences still use this concept of goal-directed activity but they are the least mathematicized of the natural sciences. Perhaps when we move from quality to quantity we necessarily lose something of the finality of nature.

             However, the most precise difference between Thomistic philosophy of nature and present-day physics probably lies in their respective notions of motion and physical activity. Aristotle's famous definition of motion occurs at the beginning of Book III of the Physics. He calls motion the 'fulfilment of what exists potentially, in so far as it exists potentially' (201 a 10). The reader will find a lengthy explanation of this definition in the first three lectiones of Aquinas' commentary. The point to be observed here is that the definition rests on a broader theory, that of potency and act, which has dropped out of modern physics. There has been a similar shift in the meaning of action. Since Newton, physics has dropped its Aristotelian correlative, passion. Instead of passion (the condition of something which is being acted on) we have reaction (simply action in a contrary direction). As a result, physical action has come to mean a sort of pure putting-forth of energy. This is the sort of event which, in the view of Aquinas, would take place only in the immaterial world!

             Finally, it may seem odd to suggest that Thomistic cosmology is closer to ordinary human experience and convictions than is modern physics. Yet this seems to be so. It is true that we now have a much greater assembly of factual data than either Aristotle or Aquinas possessed concerning the actual behaviour of physical nature. But the movement of our thinking on these data is toward theoretical construction. Our ultimate terms of analysis (waves, particles, quanta, mass, relations) are not observed facts but highly idealized structures of thought. It is quite impossible to 'picture' the physical universe as the physicist now explains it. The odd result of this constructural effort is that it seems to work. Recent theoretical developments in nuclear physics have had observable consequences of which we are all aware. These consequences appear to offer pragmatic justification for some of the most unrealistic and theoretical speculations that the world has ever known.

             St. Thomas Aquinas was a calm man, not easily startled. It is hard to say whether he would be surprised by the thinking of Einstein, Planck, Heisenberg, Born and De Broglie. What would be his attitude toward the more recent adventures of Oppenheimer, Compton, Fermi and Teller? The penetration of the atom and of outer space, the era of atomic fission, fusion, and of Sputnik--these and other achievements of modern physics might ruffle even the equanimity of Aquinas.

Bibliography

IV. BIBLIOGRAPHY

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St. Louis University    VERNON J. BOURKE