The relationship between Saint Thomas Aquinas and his sources Aristotle and Saint Augustine of Hippo illustrates a salient trait of medieval philosophy, namely, its voluntary dependence upon authorities, whose (often divergent) answers to a given problem had to be taken seriously, according to the standards of that time. Because of this, medieval thinkers attempted to solve philosophical (and theological) problems in a way that took into account all relevant sources. If an important source seemed to contradict the personal opinion of a philosopher, the philosopher then usually looked for an interpretation of that authority that could be integrated into his own solution; only in rare cases was the position of an acknowledged authority rejected. Consequently, for Aquinas, as for his contemporaries, a good theory on a certain topic had to do justice to both Aristotle’s and Augustine’s ideas on that subject, because of their authority in philosophy and theology, respectively. An examination of Aquinas’s texts on time, however, reveals a completely different picture: Whereas Aquinas expounds Aristotle’s theory at great length, he pays very little attention to Augustine’s theory. This entry provides reasons for this remarkable exception to medieval standard practices and serves as an introduction into the most important theories of time that appeared between classical antiquity and the Latin Middle Ages.
Aristotle and Augustine on Time
Aristotle’s and Augustine’s texts on time—the fourth book of Aristotle’s Physics and the eleventh book of Augustine’s Confessions—describe two theories that seem difficult to reconcile with each other: Whereas Aristotle defines time as the “number of changes in respect of before and after” (Phys. IV 11, 219b 1; R. Waterfield, Trans.) and makes its existence and definition dependent upon change or, as the medieval translations had it, motion, Augustine defines time exclusively as a “distension of the mind” (distentio animi). Furthermore, Augustine explicitly denies that motion can be an adequate definition of time and that there can be time at all without the human mind, which counts the uninterrupted stream of the sensible world. In spite of not addressing directly Aristotle’s definition (which he probably did not know), Augustine cannot have seen in it a serious option. Aristotle, on the other hand, is somewhat ambiguous regarding the relation between time and soul. He writes that there could not be time, if there is not be a soul, because without a soul there would not be any number to determine change and therefore time. However, he grants “that there might still be whatever it is that time is” (IV 14, 223a 21-29). Previously (219b 5-9) he had defined time as that number “which is numbered,” not “that by which we number,” that is, not as the mental activity of numbering, but as the flow of things that is apt for being counted, such that time should not depend entirely upon an activity of soul. Furthermore, it may well be that he is not talking here about the individual human soul but about soul as a cosmological phenomenon. Thus he would surely have rejected Augustine’s solution.
The Aristotelian Tradition Before Aquinas
As with many of his contemporaries, Aquinas’s theory of time is largely inspired by Aristotle’s solution. Aquinas’s most important discussion of that subject can be found in his Physics commentary. However, he did not have the Greek original of Aristotle’s text, but a medieval Latin translation that had been carefully corrected by his contemporary, William of Moerbeke. Indeed, it is very close to the Greek and enabled Aquinas to discuss Aristotle’s solution independently from older commentaries. This was important because the medieval understanding of Aristotle drew heavily on the interpretation that the 12th-century Arab philosopher Ibn-Rushd (Averroes) had given of Aristotle’s texts. Averroes’s interpretation rests upon the assumption that Aristotle’s discussion of the dependence of time upon the soul concerns the human soul and does not have any cosmological implications. Consequently, Averroes draws a clear distinction between an “actual time” or “perfect time” that can exist due only to the activity of the human mind, and a “potential time” or “material time” that consists simply of the changes that take place within the material world. He even stresses that outside the mind (extra mentem), “there is nothing other than something which is moved and motion.” Thus Averroes presented to medieval readers an Aristotle who is much more “Augustinian” than is the Greek original. Apart from Aristotle and Augustine, the medieval discussion relied on some further sources. Most of them (Proclus, Boethius, the Liber de causis) transmitted a Neoplatonism of the Greek type. This meant that they advocated unambiguously the existence of time outside the human mind, defining time as an image of eternity. No less important were the Latin translations of the Arab philosopher Ibn Sina (Avicenna), who discussed a whole range of explanations of time. He opted too for an extramental existence of time in the thing itself and attempted to show the incoherence of an approach that makes time dependent on an activity of the soul; thus his conception could be read as a refutation of both Augustine’s and Aristotle’s/ Averroes’s approaches. Thus medieval readers were not so much faced with an antagonism between Aristotle and Augustine; rather, there was an apparent conflict between both of them on the one hand and the Neoplatonic and Avicennian tradition on the other.
Albert the Great and
Medieval Discussions of Time
Confronted with this alternative, most medieval thinkers opted clearly for the second alternative, assuming, against Augustine and Averroes, the real existence of time outside the human mind. This was probably due to some presuppositions that were fundamental to their own religion. For a Christian, many philosophical problems were determined largely by the question of the relationship between God and humankind. What was interesting about time to medieval authors, was, then, the relation between time—the mode of duration of the sensible world—and eternity—the mode of duration of God. As the mode of duration of God’s creation, however, time had to have a form of existence outside the human mind; otherwise this creation could hardly be an image of God’s own way of existing. All these points can be found in the work of Aquinas’s teacher, Albert the Great (Albertus Magnus), who did the painstaking work of explaining the newly discovered Aristotelian writings to his contemporaries, while taking into account nearly all important earlier discussions and authorities; thus he created a synthesis that was the point of departure for many contemporary accounts of time (including that of Aquinas), even if their authors did not agree with everything Albert had said. Albert first discusses time around 1246, in his “Summa on the Creatures” (Summa de Creaturis) and again in his commentary on Aristotle’s Physics (around 1255). In both works, he reads Aristotle with the help of Averroes’s explanations. His result is that Aristotle, Averroes, and Augustine are quite close to each other, insofar as all of them reject a real existence of time outside the human soul; in this regard, Augustine seems even somewhat more radical than Aristotle and Averroes, because the last two authors grant to time at least a potential existence outside the soul. Albert, however, rejects all three approaches and sides with Avicenna and the Greek Neoplatonists, defending the real existence of time outside the soul. It exists “according to the habitual form of a distinction of the numbered elements,” as Albert concludes from the fact that the soul is counting the single elements of time, while time itself is continuously flowing. Thus Albert ascribes existence not only to permanent, unchanging entities but also to timely succession. Consequently, he openly rejects not only Aristotle’s and Averroes’s solution but also that of the church father Augustine—a remarkable case within medieval literature. Albert justifies his reproach by denying to Augustine a competence in natural philosophy. Furthermore, he affirms that the relationship between soul and time should not be discussed within the realm of physics (natural philosophy) alone but also in philosophy or metaphysics, as Averroes had already postulated. Albert himself, though, includes a lengthy discussion of time for reasons of convenience in his Physics commentary, where he adds his own treatise on eternity that differs from Aristotle’s text. Albert’s opting for a realist theory of time found many successors in subsequent periods. Even the conservative theologian Henry of Ghent (12171293) stated explicitly that Augustine’s theory of time was false. Indeed, the thesis that time has no existence outside the human soul was officially called heretical in the famous condemnation of 1277, 3 years after Aquinas’s death.
Aquinas and Aristotle
Albert’s student Aquinas depends largely on the approach of his master, especially regarding the prominent role that Aristotle must play in any discussion of that subject. But Aquinas develops two explanations of his own, both of which differ markedly from that of Albert and both of them relying on Aristotle’s Physics. This becomes clear already in Aquinas’s early commentary on The Sentences of Peter Lombard (around 1255), where he quotes the fourth book of Aristotle’s Physics in most of the relevant sections, though he discusses time, following Boethius and Albert, within the schemes of three modes of duration: time, eternity, and eviternity. In his concrete explanations of what time is, however, he follows Aristotle, in many cases as Averroes interpreted him. This holds true also for the relation between time and soul: Although the changes within the sensible world are the matter of time, its form, the numerical measure, is constituted by the human soul; thus Aquinas, at this time of his career, does not follow Albert but rather Averroes and is not so far from Augustine, whom he does not, however, quote in this context. Whereas here and in other writings only casual remarks are made regarding the problem of time, a more complete discussion can be found in Aquinas’s own Physics commentary, which was completed around 1269, 10 years after the Sentences commentary and after Albert’s Physics commentary. This commentary is, however, quite different in form from Albert’s, because Aquinas confines himself to explaining the content of Aristotle’s text without any lengthy discussions like those that had been given by Albert to help clarify Aristotle’s position. Consequently, Aquinas’s commentary sticks much closer to Aristotle’s own statements, without mentioning by name authors such as Averroes, Avicenna, and Augustine. Concerning the relationship between time and soul, Aquinas interprets Aristotle’s solution as implying the existence of time, even if there would not be any soul that could count it. Only the act of numeration, not the existence of the things that are numbered and not the existence of the number itself, depends on the existence of soul. This new interpretation of Aristotle’s text was possible because Aquinas could use the improved translation by William of Moerbeke, who rendered the sentence quoted earlier in this entry as “that there might still be that time is somehow being (utcumque ens),” suggesting that time should have some extramental reality. However, Aquinas further qualifies his position by saying that only the indivisible aspect of time exists in reality (i.e., a single instant of time), whereas time itself, not different from motion, has no firm being (esse fixum) in reality. Consequently, time receives its totality (totalitas) by “the ordering of the soul which numbers the before and after of change.” Consequently, without the numbering soul, time exists only imperfectly (imperfecte). While this formulation resembles Averroes’s solution, Aquinas differs from him by acknowledging that time does not only potentially exist outside the soul and by not mentioning the distinction of matter and form in this respect. Thanks to Moerbeke’s improved translation, Aquinas is able to ascribe this solution to Aristotle himself, while Albert still reproached Aristotle together with Averroes and Augustine for denying to time its existence outside the soul.
Aquinas and Augustine
Augustine, unlike Aristotle, was not an important source for Aquinas’s theory of time. In fact, in Aquinas’s discussions of the problem, the name of Augustine appears rarely, and there are no quotations of the 11th book of the Confessions. This has been interpreted as a consequence of Albert’s critics of Augustine’s theory of time and of his assumed lack of competence in natural philosophy, but it may also be due to the methodical presuppositions of Aquinas’s Physics commentary. In any case, it must have been convenient for Aquinas not to mention that his theory of time was implicitly criticizing the authority of Augustine; with Averroes, a renowned but ambivalent philosopher was at hand who could be criticized for advocating the unacceptable theory that the existence of time depends upon the human soul. There was no necessity to mention the venerable church father Augustine in such unreliable company.
See also Albertus Magnus; Aquinas, Saint Thomas; Aristotle; Augustine of Hippo, Saint; Eternity; Ethics; God and Time; Metaphysics; Ontology; Teleology; Time, Sacred
Barnes, J. (Ed.). (1991). Complete works of Aristotle (Rev. Oxford Trans., Vols. 1-2). Princeton, NJ: Princeton University Press.
Davies, B. (1993). The thought of St. Thomas Aquinas. Oxford, UK: Oxford University Press.