Aquinas’ Metaphysics and Aristotle’s Arguments for the Eternity of the World
/By John F. X. Knasas
University of St. Thomas, Houston, TX
In a Thomistica review of my book, Thomistic Existentialism and Cosmological Reasoning, John Brungardt disputes my claim that Aquinas neutralizes the arguments for the eternity of motion and time through an already in place metaphysics, and so without that metaphysics, the philosopher, who at this point is only a philosopher of nature, would erroneously concluded that the world is eternal.[1] Brungardt argues that the natural philosopher by his own lights can do this neutralizing, and so from the perspective of the natural philosopher the eternity of the world is not a demonstrated truth and the natural philosopher would not erroneously think otherwise.
Before I reply to Brungardt’s critique I want to note the stakes involved. Nothing less is involved than the understanding of the doctrinal unfolding of the philosophical sciences. If we need an already in place metaphysics to critique the eternity arguments, then it appears that we can do metaphysics before we do natural philosophy. Such a position is anathema to a long, but not unanimous, tradition in Thomistic interpretation. Proponents include Benedict Ashley, James Weiseipl, William Wallace and others.[2] According to these Thomists, the conclusion of something immaterial in natural science, for example, the first mover or the rational soul, justifies our negative judgment that the meaning of being is not necessarily material. This negatively modified understanding of being is the subject matter of a new science, metaphysics. Without this prior philosophizing, Thomistic metaphysics cannot critically secure its scientific status and becomes mere poetry.
In the 20th century Thomistic revival various authors in various ways critiqued the linkage of metaphysics to natural philosophy. Jacques Maritain, an existential Thomist, attained the third degree of abstraction, on which we find metaphysics, by finding something in the positive judgment of esse (l’intuition de l’être) to ground the negative judgment that esse is not necessarily material. Joseph Maréchal, the founder of Transcendental Thomism, turned to the mind’s innate intellectual dynamism to Infinite Being to formulate the negatively immaterial notions of metaphysics. Finally, Etienne Gilson and especially his student, Joseph Owens, questioned that common Scholastic assumption that metaphysics must be initiated by attaining the third degree of abstraction. Sufficient to initiate the science of metaphysics was simply the judgmental grasp of esse in sensible things. I have previously discussed these positions.[3] At present, I want to point out that Aquinas’ criticism of the eternity of motion suffices to decouple metaphysics from natural philosophy and to establish the autonomy of Thomistic metaphysics, for better or worse.
Second, if the critique of these arguments must be metaphysical, then without metaphysics the natural philosopher is doomed to erroneously conclude that motion, and hence the world, is eternal. That outcome would have someone like the saintly Aquinas teaching heresy. In Aquinas’ medieval faith, the Church taught that God created the world in time. Brungardt might scoff at these implications, but I will argue that more than he realizes, they lurk more proximately to his position.
In section 4 of his review, Brungardt focuses on Aristotle’s third argument for the eternity of motion. This argument is from motion’s measure of time. The argument states that time is inseparable from the now. The now, however, is an intermediate. Hence, there is time before the now and after the now. (982) Brungardt echoes Aquinas’ critique of the argument. Intermediates, or middles, can be extremes. For example a point can be the terminus of a line as well as an intermediate of a line. Only if we assume time to be eternal, do we know that every now is a middle. (983) Hence, the argument fails because it begs the question.
Brungardt extrapolates the critique to neutralize the thesis that every generation of one thing is the corruption of another. Matter is another middle and so its continuity is not a requirement for generation. In these ways the natural philosopher by his own lights would discern the possibility of an absolute beginning of time and of existence.
As lucid as these reflections are, a more attentive reading of the Aquinas’ Physics commentary would belie them. Brungardt’s understanding of the third argument is incorrect. Brungardt’s interpretation of the third argument, Aquinas says, is Averroes’ interpretation. Aquinas says the notion of the now as a middle does not agree with Aristotle’s intention. (984) The correct starting point is the understanding of the now as a beginning and as an end. Aquinas explains, “And so it must be said otherwise, according to Aristotle’s intention (secumdum intentionem Aristotelis), that this, that the now is a beginning and an end, he wishes to take from what he first supposed, namely, that a before and after is not, time not existing.”[4] Aquinas goes on to explain:
If it is given that some now is the beginning of some time, it is clear from the definition of beginning, that the beginning of time is that before which nothing of it exists. Hence, it is to accept some before or prior than the now itself that is maintained to be the beginning of time. But the prior is not without time: therefore the now that was posited the beginning of time, is also the end of time. And in the same way if there is posited a now to be the end of time, it would follow that there is also a beginning because from the notion the end is that after nothing of it is. The after, however, is not without time: Therefore it follows that the now that is the end is also the beginning of time.[5]
In sum, since you cannot have a beginning without a before nor an end without an after, then both the start and end of the now involves prior and posterior time. Hence, you cannot consistently think a beginning and an end of time. So time is eternal.
If this is the true nature of Aristotle’s third argument according to Aquinas, then what is Aquinas’ reply? Aquinas claims that when we think a before and after for the now as a beginning and as an end, the before and after are not real but imaginary only. (990) Similarly, when we think a beyond or an outside to the universe, the extra-cosmic beyond is only imaginary. Aquinas does not seem to be saying that time before time and space beyond the cosmos may be imaginary. His claim is more straightforward, They are imaginary. In truth before time is the divine eternity and outside the universe is the divine magnitude. Apparently Aquinas has his reasons. At S.T. I, 7, 3, Aquinas argues from natural philosophy theses that a natural body is finite in magnitude. That would be a reason for claiming that outside the cosmos is imaginary space. One would suppose that Aquinas also has an argument for his claim about imaginary time. What might that argument be?
Aquinas frequently argues for the eternity of God from the absolute immobility of God. For example, C.G. I, 15 and S.T. I, 10, 2. In the Physics VII commentary he does present Aristotle giving an argument for a first unmoved mover. It is the same argument that Aquinas presents as the prima via in the Summa Contra Gentiles and the Summa Theologiae. In sum, what is moved is moved by another. Therefore, an unmoved mover exists or we proceed to infinity with moved movers. An infinite regress of moved movers, however, is impossible. Therefore, an unmoved mover exists and is God. So the case can be made that this argument that Aquinas finds in Physics VII is the reason to which Aquinas appeals in his critique of the third argument for motion’s eternity.
For purposes of this article, the paramount question is whether the argument of Physics VII is a natural philosophy argument or a metaphysical one. One can concede that the argument for imaginary space is a natural philosophy argument. A reader would then be inclined to regard the reason for imaginary time to be a physical reason also. That physical interpretation of the reason would save Brungardt’s general position; namely, while staying within the bounds of natural philosophy one can defuse the third argument for the eternity of the world. In my opinion, however, since his interpretation of the third argument was incorrect, then his interpretation of Aquinas’ critique cannot be extrapolated to criticize the first two arguments for the eternity of motion.
So what kind of argument is Aquinas presenting in Physics VII? In my book I argued that the reasoning of Book VII could not be physical and philosophically successful. Hence, that argument should be glossed metaphysically.[6] In sum, a motion will lead vertically to something unmoved. For example, the rock is moved by the stick, the stick by the arm, the arm by the man, the man by the soul. That something unmoved may well be something produced by a previous generation. For example, the soul comes to be in the generation of the man. But now we are involved in a lateral regress of generators that may well go back infinitely.[7] So, the natural philosophy interpretation of the reasoning of Book VII cannot get back on track without dealing with the eternity of the world. That does not happen in the reasoning and so a natural philosophy interpretation of it is doubtfully what Aquinas had in mind when he used it to prove God.[8]
In this article I would like to provide another reason for a metaphysical reading of the reasoning of Book VII. Back at In II Phys. I. 11, 243, Aquinas describes the consideration of an immobile mover as a third philosophical study. It assigns the study to metaphysics:
Certain things are immobile and around this is one study of philosophy. Another study of it is around those things that are mobile but incorruptible, as are celestial bodies. A third study of it is around mobiles and corruptibles, just as are inferior bodies. And the first study pertains to metaphysics, the other two to natural science. (243)
Aquinas characterized the consideration of a wholly unmoved mover to be a consideration of metaphysics. Aquinas does not divide up the consideration of the absolutely unmoved mover. It is the affair (negotium) of metaphysics only. Surely if natural philosophy proved the unmoved mover, Aquinas would have acknowledged it here, just as he acknowledges that natural philosophy considers the incorruptible celestial bodies. In paragraph 245, Aquinas reiterates, “Natural philosophy does not consider every mover. … And such is the moving principle which is altogether immobile and the first of all movers, as will be shown in Book VIII.”
I will consider the reference to Book VIII in a moment, but Aquinas’ philosophical or doctrinal point in these two texts from Physics II is that the wholly unmoved and first mover does not belong to natural philosophy but to metaphysics. Hence, the proof for the unmoved mover in Book VII must be understood metaphysically. What that understanding would look like I have detailed in my book with my glosses of the prima viae in both Summae. I will not repeat them now. I will note that as interpreted metaphysically the Book VII motion proof would reach an unmoved mover that is subsistent esse and as such would also be a creator. The Book VII proof would then be Aquinas’ warrant for bringing in a creator to defuse the first two proofs for motion’s eternity in Book VIII.
Finally, why did Aquinas locate the proof of the absolutely unmoved mover just to Book VIII? Should not Aquinas have said Book VII or Book VII and VIII? The answer may be Aquinas’ remark at the beginning of Book VIII.
For in the proceeding books, Aristotle spoke of motion in common [in communem], not applying to a thing; now, however, inquiring whether motion has always been, he applies the common consideration of motion [communem considerationem motus] to the being [esse] that it has in things. (967)
Aquinas says that Aristotle is going to take his general comments on motion and apply them to things. In other words, the reasoning of Book VII does not contain the assertion that motion exists and so strictly speaking, is not a proof. Somewhat similarly it was once argued that the De Ente reasoning from “What belongs to a thing is caused. . .” was not a proof for God because it did not contain the assertion that things exist. [9] Shortly after in Book VIII (967) Aquinas admits that it is a deficiency that can easily and quickly be addressed. As so close to a proof, it can be considered a proof as well as not a proof. Interestingly, the versions of the Book VII reasoning in the prima viae of the two Summae begin with the assertion that motion exists.
In conclusion, if one relentlessly hunts down the thinking behind Aquinas’ critique of motion’s eternity from the eternity of time one will still find the metaphysician doing the speaking.[10] This critique means that without a metaphysics already in place, the natural philosopher can only affirm motion’s eternity.
[1] “At the Heart of Being: Thomistic Existentialism and Cosmological Reasoning,” at Thomistica.net. My publication is Thomistic Existentialism and Cosmological Reasoning (Washington, D. C., The Catholic University of America Press, 2019).
[2] For references and citations, see John F. X. Knasas, “Aquinas on the Cognitive Soul: Metaphysics, Physics, or Both?,” American Catholic Philosophical Quarterly 72 (1998): 501-2, n. 2; also John F. X. Knasas, “The Role of Sense Realism in the Initiation of Thomistic Metaphysics,” ed. Christopher M. Cullen, SJ and Franklin T. Harkins, The Discovery of Being & Thomas Aquinas: Philosophical and Theological Perspectives (Washington, D.C., The Catholic University of America Press, 2019), 66-7, n. 11.
[3] See John F. X. Knasas, Being and some Twentieth-Century Thomists (New York, Fordham University Press: 2003), 45-70.
[4] In VIII Phys, lect.2, no, 984. My translations throughout.
[5] Ibid.
[6] I provided that gloss in my interpretation of the prima via in C.G. and S.T. See Knasas, Thomistic Existentialism, 218-28, and 251-56.
[7] Knasas, Thomistic Existentialism, 232-236. Anthony Kenny and Scott MacDonald see a similar problem with the argument of Phys. VII. For Kenny, see ibid., for MacDonald, see ibid.
[8] In his “The Conclusion of the Prima Via,” ed. by John R. Catan, St. Thomas Aquinas on the Existence of God; the Collected Papers of Joseph Owens (Albany: State University of New York, 1980), 145-7, Joseph Owens notes a metaphysics background for Aristotle’s claim that no body can be in motion primarily and per se. The metaphysical reference is that a cause is what is first and primary. The explanation of this claim is found in In II Meta., lect. 2, nn. 292-6: a cause of an attribute is what has the attribute per se and is highest in the genus. I would only add that these claims and be traced further back to the De Ente et Essentia reasoning for a first cause of esse that is intelligibly one with its esse.
[9] “In point of fact, the reasoning [of the De Ente] does not commence with the assertion that something exists. . . . From that viewpoint one may say that the De Ente et Essentia does not contain a proof for the existence of God.” Joseph Owens, op. cit., 181.
[10] For a discussion beyond the Physics about which science demonstrates God according to Aquinas, see Knasas, Thomistic Existentialism, ch. 6.