This paper seeks to explore the central role of God within Aristotelian metaphysics. It will be argued that, for Aristotle, the discovery of God in Book VIII of the Physics is necessary for entering into first philosophy. In order to scientifically investigate being as being—in order to move beyond the study of mobile being and onto the study of being as such—one must first demonstrate the existence of immaterial being. For Aristotle, this is equivalent to proving the existence of God. In other words, metaphysics is the fruit of physics: in having to appeal to God as a principle in explaining the activities of material beings, we are led into a wider consideration of the nature of being as a whole. Moreover, it is God’s ontological priority among substances—and his explanatory role in the cosmos—which legitimizes metaphysics as a philosophical science. Thus, a true Aristotelian must understand metaphysics to be nothing other than a sort of theological philosophy. It is this science in which the philosophy of nature necessarily terminates.
Now for Aristotle a science is a state of the soul in which it grasps the truth of things in terms of their proper causes through demonstration.1 Physics, or the philosophy of nature, is the science which investigates the natural order. Since the physical world is defined by materiality and mobility, physics can be understood as that science which studies material beings insofar as they are mobile: it the science of mobile being qua mobile.2 Indeed, the reality of change is the primary starting point for the philosopher’s inquiry into nature.3 Thus, physics is that science which, accepting the reality of motion as evident, seeks to render it intelligible to the human mind by appealing to a variety of philosophical principles such as act, potency, form, matter, and so on.4 These principles are discovered in the philosopher’s initial analysis of change but go on to serve as the explanatory apparatus of his general investigation into the whole architecture of nature. Moreover, such principles are carried over into the higher, more exalted sciences like metaphysics. Thus, philosophical science moves from a study of those realities which are most evident to our senses (i.e. motion) and proceeds to an inquiry into those realities which are most intelligible in of themselves but least intelligible to us (i.e. the first causes of being).5
In Book 8 of the Physics, Aristotle demonstrates that in order to philosophically account for the motion we observe in nature we must posit the existence of an immaterial and everlasting substance who is the source of all of the activities of natural substances. This ultimate cause of change, this unmoved mover, is identified with God.6 Thus, the investigation which is the centerpiece of physical science—the analysis of the principles of change—points beyond itself in appealing to a reality which eludes its scope of inquiry: in philosophically analyzing the movable, we are forced to assert the existence of the immovable. This argument represents the transition from physics to metaphysics and from cosmology to theology. For it is here that the entirety of being, not merely material and mobile being, is opened up to philosophical scrutiny; it is here that metaphysics, the study of being as being, is introduced. Physics, if it is to complete its own task of giving a scientific account of motion, must eventually terminate in the discovery of a reality which grounds and demands a science of its own.
Aristotle introduces his argument for the necessity of the unmoved mover by first arguing that motion must be everlasting and continuous on the grounds that admitting the possibility of a temporal beginning of motion results in absurdity: since time is the measure of motion in terms of before and after, it is wholly incoherent to say that there was a time before time. And because time cannot come into being, motion cannot come into being, because time is nothing other than the measure of motion: “how can there be any ‘before’ and ‘after’ without the existence of time? Or how can there be any time without the existence of motion? If, then, time is the number of motion or itself a kind of motion, it follows that, if there is always time, motion must also be eternal.”7 As we will see, this initial preliminary point will prove important for Aristotle’s understanding of both God’s role in the universe and the divine attributes he infers from God’s causation of everlasting and continuous motion.8 Having accepted motion as evident to the senses and asserted its perpetuity and continuity, Aristotle then forwards a philosophical principle which serves as an essential premise in his argument for the unmoved mover: everything that is moved is moved by another. This in fact follows from his definition of motion as “the fulfillment of what exists potentially, in so far as it exists potentially”9 or “the fulfilment of the movable in so far as it is movable.”10 Motion for Aristotle is understood in terms of act and potency.11 That is, motion is nothing other than the reduction of a potency to actuality. But to be movable, to be capable of acquiring a particular actuality, a being must be in potency with respect to some actuality it does not currently possess. Hence, it is impossible for a being in potency to give itself the actuality it is in potency towards precisely because it is in potency towards it i.e. it does not yet possess it, and something cannot give to itself what it does not already have. If it could reduce itself to actuality, it would have to already possess this actuality, which would entail that it could be in potency and actuality in the same respect and at the same time. But this is an impossibility.12 Thus, something in potency can only be moved to act by something else which is already in act. If a being is moved, it is necessarily moved by another.
Aristotle secures this principle as certain by analyzing different kinds of motion and demonstrating how this principle applies.13 In the case of bodies which are moved contrary to nature, it is abundantly obvious that they are moved by another; but Aristotle also insists that the principle applies in the natural motion of beings which appear to be self-movers, like animals. The trouble is not whether or not there is a real distinction between a moved and a mover within a self-mover but rather how we are to go about identifying and distinguishing the two within a single substance:
“The fact that a thing that is in motion derives its motion from something is most evident in things that are in motion unnaturally, because in such cases it is clear that the motion is derived from something other than the thing itself. Next to things that are in motion unnaturally those whose motion while natural is derived from themselves—e.g. animals—make this fact clear: for here the uncertainty is not as to whether the motion is derived from something but as to how we ought to distinguish in the thing between the mover and the moved. It would seem that in animals, just as in ships and things not naturally organized, that which causes motion is separate from that which suffers motion, and that it is only in this sense that the animal as a whole causes its own motion.”14
Thus, apparent self-movers like animals move themselves only because one part of them moves another.15 It is the case of elemental motion in which the principle proves most difficult to apply.16 However, the apparent difficulties can be overcome once we distinguish different senses of potency and thus different causal factors involved in elemental motion.17 Once this is accomplished, we have brought all kinds of motion under the aegis of the axiom ‘whatever is moved is moved by another.’ Now if this is true—if there is motion, and if each thing that is moved is moved by another—then we must eventually come to a first term in the sequence of movers which explains the motion of the subsequent members. Aristotle is convinced that an infinite series of movers is an impossibility for the simple reason that without one we will find no explanation for how the entire series is causally efficacious in the first place.18 He makes this concrete by using the example of a stick moving a stone which is in turn moved by a hand; in this case, we have a series of intermediate links of movers, all of which are totally dependent on a prior mover for itself moved by something else, since in an infinite series there is no first term.”
their respective movements.19 If the man ceases to move the stick with his hand, the stone will cease to be moved as well; the later members depend upon the earlier ones.20 If there is no first mover, the other movers in the causal chain will not be able to impart motion of their own. Aristotle restates these points by interweaving them in a singular passage which is worth quoting at length:
Every mover moves something and moves it with something, either with itself or with something else: e.g. a man moves a thing either himself or with a stick, and a thing is knocked down either by the wind itself or by a stone propelled by the wind. But it is impossible for that with which a thing is moved to move it without being moved by that which imparts motion by its own agency: on the other hand, if a thing imparts motion by its own agency, it is not necessary that there should be anything else with which it imparts motion, whereas if there is a different thing with which it imparts motion, there must be something that imparts motion not with something else but with itself, or else there will be an infinite series. If, then, anything is a mover while being itself moved, the series must stop somewhere and not be infinite. Thus, if the stick moves something in virtue of being moved by the hand, the hand moves the stick: and if something else moves with the hand, the hand also is moved by something different from itself. So when motion by means of an instrument is at each stage caused by something different from the instrument, this must always be preceded by something else which imparts motion with itself…So this reasoning also shows that when a thing is moved, if it is not moved immediately by [a first mover], the series brings us at some time or other to a mover of this kind.2121 We can break down this passage as follows. If something produces motion by itself, then it will be a first mover; but if something only causes motion by itself being moved by another mover in a sequence of intermediate movers, we will also have to arrive at a first mover. For in a series of instrumental causes—as, for example, in the case of a stone moved by a stick which is moved by hand—the motion of the later members is derived from the causal power of the earlier ones. If then, something causes motion by being moved by another (which has been proven to be the case in all things which are moved) there will have to be a first term in the series of movers because intermediate movers only have the power to impart motion in a derivative way and, as such, are dependent on a mover which produces motion in a non-derivative way. Since their power to move is derivative, there must be something from which they derive it from. Thus, either movement is caused immediately by a first-mover or it is caused by a mover who is the first term in a series of intermediate movers. Either way we will have to arrive at some first mover which is itself unmoved.22 But if there is an unmoved mover—and we have now, according to Aristotle, demonstrated that there has to be if we are to provide a scientific account of the motion evident to our senses—this being must be everlasting. For motion, as it has been proved earlier, admits neither of origin nor cessation. But perishable things—substances subject to generation and corruption—cannot explain a motion which is continuous and unceasing. Thus, we must suppose that the first mover of the cosmos is just as everlasting as the motion it produces.23 Furthermore, we need not posit more than one unmoved movers, since nature prefers a finite set of conditions to an infinite set of conditions in producing the same result; it is therefore sufficient to assume only one prime mover as the first cause of all cosmic motion.24 Such an eternal being cannot be cannot be composed of parts nor defined by material extension. For if the first mover did have a magnitude it would be either a finite or an infinite magnitude: the first option is untenable, as it fails to explain an infinite motion in an infinite time; the second is an intrinsic impossibility, since actual infinities do not exist.25 Hence, we have arrived—through a careful and sustained philosophical reflection on the reality of motion—at an immaterial and eternal substance which is the origin of all motion in the entirety of the universe. Our study of being in motion leads us to the discovery of a reality which is itself unmoved; in accounting for the principles of mobile being, we discover the existence of immobile being.
Thus, physics culminates in the unearthing of a strata of being which eludes its scope of study. Eternal and immovable being, necessary to postulate in order to philosophically explain motion, lies outside the range of the physical sciences. And so, recognizing that being is not restricted to the transient and the movable, Aristotle undergoes the construction of new science which studies not being as merely material and mobile but being as such: being as being. This science will study the first principles of the entirety of reality, both material and immaterial; and this science, which is founded upon a philosophical proof for the existence of God, can be called not only metaphysics but also theology: But if there is something which is eternal and immovable and separable, clearly the knowledge of it belongs to a theoretical science—not, however, to physics (for physics deals with certain movable things) nor to mathematics, but to a science prior to both…[T]he first science deals with things which both exist separately and are immovable…There must, then, be three theoretical philosophies, mathematics, physics, and what we may call theology, since it is obvious that if the divine is present anywhere, it is present in things of this sort… For one might raise the question whether first philosophy is universal, or deals with one genus, i.e. some one kind of being…We answer that if there is no substance other than those which are formed by nature, natural science will be the first science; but if there is an immovable substance, the science of this must be prior and must be first philosophy, and universal in this way, because it is first. And it will belong to this to consider being qua being—both what it is and the attributes which belong to it qua being.26
Here, Aristotle gives a basic description of the shape and nature of the metaphysical enterprise. First, Aristotle claims that if there is a science which considers the immovable it cannot belong to physics which, by definition, deals strictly with the movable. We see then that metaphysics is founded upon a particular negative judgment: being is not restricted to the material and mobile; being as such—and more particularly, eternal, immaterial, and immovable being—requires a science of its own. Secondly, the science which deals with the immovable will be called theology since it considers those realities which are most divine. First philosophy, therefore, is in its very conception a study primarily concerned with God. But it must be asked, Aristotle notes, whether or not first philosophy studies a single genus. For reasons having to do with the nature of logical definition and demonstration, each particular science is usually restricted in scope to a single genus of being. But, as Aristotle not only asserts but spends a considerable time proving, being is analogous and not a genus of its own.27 It would seem then, that a science which studies being as being would be an impossibility; such a study would, under most circumstances, not be genuinely scientific according to Aristotle’s own criteria for philosophical knowledge. In response to this puzzle Aristotle simply answers that, if immovable being did not exist, physics would be the highest science and accorded the title of first philosophy rather than metaphysics.28
It seems then, that in response to the question “how can metaphysics be a genuine science if being is not a genus?” Aristotle simply gestures at the fact that God exists. In order to elucidate this initially puzzling claim—and get a better grasp on why first philosophy is theology—we must launch a deeper investigation into both Aristotle’s conception of ontological priority within being as well as his understanding of the significance of God’s causal primacy in the cosmos. Now for Aristotle, there is still a certain unity to being despite it not constituting a single genus. Being is divided into various categories—substance, quality, quantity, relation, etc.—but among these categories substance holds both existential and explanatory priority. For all of the other categories exist only by adhering in, and therefore being predicated of, substances. Indeed, “it is in virtue of this category [i.e. substance] that each of the others also is.”29 In the order of being, substance is primary in that it alone is separable, whereas the other categories are dependent upon substance for their existence: “of the other categories none can exist independently, but only substance.”30 Thus, “that which is primarily, i.e. not in a qualified sense but without qualification, must be substance.”31 In the order of knowledge substance is also prior to the other categories since “we know each thing most fully, when we know what it is, e.g. what man is or what fire is, rather than when we know its quality, its quantity, or its place.”32 Substances are essential even to basic definitions.33 And so, since substance is the core of being, and is most central to our knowledge of it, Aristotle can say that “the question which was raised of old and is raised now and always, and is always the subject of doubt, viz. what being is, is just the question, what is substance?”34 Because all beings are either substances or affections of substance—because all other features of reality are referred back to this one—we can say that being is primarily substance. Thus, recognizing the centrality of substance to the categories is the first step in justifying a science of being as such:
Being is meant in multiple ways…but with reference to a single core. Some things are called beings because they are substances, others because they are affections of substances, others because they are a path to substances or are destructions or privations of substance, or belong to things spoken of in relation to substance, or negations of some one of these or of substance itself…For there is a single science for investigating not only those individuals spoken of as one, but also when individuals are spoken of as related to a common nature; for these too are, in a certain way, spoken of as one. It is also clear, then, that it falls to a single science to investigate beings insofar as they are beings. And in every case, science investigates most centrally what is primary, that upon which other things depend, because of which they are spoken of. If then, this is substance, the philosopher must possess the principles and causes of substances.35
The centrality of substance is the first stage in the scientific unification of being, then, for two reasons. First, every other category besides substance depends upon substance for its existence. Second, every claim about any aspect of being is going to, at bottom, make reference to substance—to say, for instance, something about a particular quality, quantity, or relation is ultimately to qualify substance. Thus, to give an exhaustive account of substance is nearly equivalent to giving an exhaustive account of being. For these reasons—all hinging upon substance’s priority to all other categories—Aristotle thinks that investigating being as being will focus chiefly on a philosophical understanding of substance: “It is clear then, that if it falls to one science to investigate being qua being as well as those things belonging to it qua being; the same science will investigate not only substances but also things belonging to them.”36 But the identification of substance as the core of being will only get us so far; for it could very well be the case that the world is made up of a variety of substances which have nothing, or at least very little, to do with each other ontologically. Even if substance is primary within being, it is still the case that substances themselves may not be incorporated into a common ontological picture which thoroughly justifies a science which studies them as whole. In order to integrate the totality of substances into a singular philosophical framework, we must investigate further metaphysical priorities among beings and see how these can be fit into a common explanatory structure which constitutes a scientific body of knowledge of the entirety of reality. The first thing to understand is that, within substance itself, there is a priority of actuality over potentiality and of the eternal over the corruptible.37 Because of this priority, substance is more properly identified with the actuality of form over the potentiality of matter since the material principle in concrete sensible substances cannot be shaped into an intelligible concrete being without the principle of act that is form.38 Thus, among the categories substance is primary and within substance actuality and form is primary—and therefore more properly identified with substance. Act and form are the most foundational aspects of reality, since they are the most foundational aspects of substance; moreover, it is act and form which are shared by all beings in the universe regardless of whether or not they are material and mobile or immaterial and immovable. It is substance as actuality and form which is common to being as being.
Hence, the science of metaphysics can focus most specifically on act and form as the common basis of the variety of substances in the world, and that which is most ontologically fundamental to them. But, as we have seen within book 8 of the Physics, the actuality that is exercised in the natural world is derivative. The argument from motion has already demonstrated that, in order for composite substances to exercise their own actualities there must be an immaterial substance whose very nature is actuality. In other words, the actuality of sensible substance depends on the actuality of a divine substance: “But if there is something which is capable of moving things or acting on them, but is not actually doing so, there will not necessarily be movement; for that which has a potency need not exercise it…There must, then, be such a principle, whose very essence is actuality. ”39 The first principle of act in the cosmos is God, who is the source of the actuality of all other things; the actuality of substance is primary within being, but God—as pure act—is primary among all the substances. As such, he is the first principle and cause of all substances which exist: “On such a principle, then, depend the heavens and the world of nature.”40
We can see then that in the same way that all of the categories are referred back to substance as their principle and cause, so all of the substances are referred back to God as their principle and cause; in the same way that substance unifies all of the categories of being, God unifies all of the substances in the world. And this priority is parallel to the priority we found in substance which was both existential and explanatory. On the one hand, God is first in the order of being in a very direct way: he is the eternal substance from which all other substances derive their activity. If substance is primary among the categories, and actuality is primary within substance, then God, who is the pure actuality from which all other substances derive their actuality, is the primary substance—the substance upon which all other substances depend. But God is also essential in explanation. For it is his causal action which unifies the cosmos into a cohesive picture open to philosophical analysis. We have seen that God’s explanatory role in the universe allows us to make sense of the actualities of substances and thereby affords us a first principle by which we can philosophically explicate their activities. But his causal action also ensures that the universe, the totality of substances which exist, are organized in such a way that we can analyze the entirety of substances as ontologically linked within a common system and thereby can study not just individual substances but also their integrity as a sum total—we can philosophically investigate “the nature of the whole.”41 We can observe the unity of the cosmos which emanates from the casual action of God as follows. First, we notice a cohesion to the celestial bodies which can be detected in astronomical observations but which is ultimately traced back to their dependence on God who is the source of their movement as final cause, that is, as an “object of love.”42 Second, there is a unity of the heaven with the natural world which is indicated most obviously in the dependence of the activity and features of natural beings on the seasons, which are in turn dependent on the motion of celestial substances.43 Third, the natural world exhibits a cohesion which is most easily noticed in the patterned regularities in the natural order, especially the manner in which natural substances are adapted to each other and are therefore interconnected within the common frame of nature.44 In other words, there is a deep integration and unity among all substances within the universe which can be traced back to the activity of God as the first cause; the world’s order is sustained eternally and continuously by a divine substance, a first principle who imbues the functions of all substances with the intelligibility of a single metaphysical structure. The entirety of substances, whether corruptible like natural substances or incorruptible like celestial ones, are governed by “one ruler” who organizes and integrates all facets of being into a unity, into a single ontological regime which can be compared to an “army” and a “household.”45 And so we can now understand why it is that Aristotle insists on the identification of first philosophy—the study of being qua being—with theology. The discovery of God’s existence in the culmination of the Physics opens up the possibility of an inquiry into being as a whole in demonstrating that being is not restricted to the material; but God’s ontological and explanatory primacy within being is also what justifies metaphysics as a science. For it is God who unites all beings into a common universe as their shared first principle, and thereby unites all beings into a structure worthy and admittable of scientific study. As the first cause of beings, as the primary substance, God grants a unity to being sufficient for it to meet the criteria for a scientific object. As we have seen in Aristotle’s remarks on substance, even though a science usually studies something spoken of in one way univocally i.e. as a single genus, it can also study something spoken of in one way as related back to a common referent—a first principle and cause which incorporates them into a single explanatory structure. Substance initially performs this function for the categories, but it is God who provides this function for all of the substances. Theology then, as first philosophy, does not study being as a single genus but rather studies it in relation to its first substantial principle: God. It is by understanding beings not as in accord with one thing but in reference to one thing—the divine substance which is their first cause—that we acquire scientific knowledge of being as such. Metaphysics, therefore, is the study of being as being only because it is the study of God’s priority among beings; and the philosopher, who acquires theoretical wisdom by ordering all things in accordance with first principles through demonstration, ascends to the highest state of knowledge when, after progressing through the various stages of philosophical science, he finally orders all things whatsoever according to their ultimate first cause—that is, when he sees all things in relation to God.
Bibliography
Aristotle. Physics. Translated by R. P Hardie and R. K. Gaye. In The Basic Works of Aristotle, edited by Richard McKeon (New York: The Modern Library, 2001).
———. Prior Analytics. Translated by A. J. Jenkinson. In The Basic Works of Aristotle, edited by Richard McKeon (New York: The Modern Library, 2001).
———. Metaphysics. Translated by W. D. Ross. In The Basic Works of Aristotle, edited by Richard McKeon (New York: The Modern Library, 2001).
Gerson, Lloyd P. Aristotle and Other Platonists. Ithaca/London: Cornell University Press, 2005.
Reeve, C. D. C. Aristotle’s Theology: The Primary Texts. Indianapolis/Cambridge: Hackett Publishing Inc., 2022. Shields, Christopher. Aristotle. Second edition. London/New York: Routledge, 2014.
- In the Prior Analytics, Aristotle defines science as “Certain and evident intellectual knowledge of things in terms of their proper causes” (71b8-18). Knowledge is certain and evident when a) what is known appears clearly to the intellect and b) a proposition can be accepted as true without fear of error. This certainty is attained by logical demonstration. The framework of causal explanation is primarily to be understood in terms of the Aristotelian fourfold schema of causes, which provides the mind with why something is the case, not merely that it is the case: “Now, the causes being four, it is the business of the [philosopher] to know them all, and if he refers his problems back to all of them, he will assign the ‘why’ in the way proper to his science—the matter, the form, the mover, ‘that for the sake of which’” (Physics 198a22-25). Scientific knowledge is not merely a body of propositions but also an intellectual virtue perfective of human nature (See: Nicomachean Ethics, Book VI). Unless otherwise noted, translations are from The Basic Works of Aristotle, edited by Richard McKeon (New York: The Modern Library, 2001). ↩︎
- Physics 198a29-31 and Metaphysics 1026a12. ↩︎
- “Now the existence of motion is asserted by all who have anything to say about nature, because they all concern themselves with the construction of the world and study the question of becoming and perishing, which processes could not come about without the existence of motion” (Physics 250b15-18). ↩︎
- Aristotle is clear that the philosopher of nature must take the reality of motion as evident to the senses: “We physicists must take for granted that the things that exist by nature are…in motion, which is made plain by induction” (Physics 185a13). ↩︎
- Of course, the study of logic is the first science with which the philosopher must be equated since it deals with the division and method of the sciences and lays the foundation for all philosophic inquiry in providing the rules by which the mind can be led to the acquisition of truth. Mathematics comes second, and the philosophy of nature comes third. The last in execution—but the first in honor—is metaphysics. For a succinct explanation of the Aritotelian-Thomistic approach to the ordering of the sciences see: Thomas Aquinas, Commentary on the Book of Causes, trans. Vincent A. Guagliardo, O.P., Charles R. Hess, O.P., and Richard C. Taylor (Washington D.C.: Catholic University of America Press, 1996), Preface, 3-4. ↩︎
- The identification of the prime mover with God is implicitly hinted at in the Physics but happens most explicitly in the Metaphysics. ↩︎
- Physics 251b10-15. See also: Metaphysics XII 6 and 7. Aristotle’s overarching argument for the perpetuity of motion has been formalized by Christopher Shields in (Aristotle, 2nd ed. [New York: Routledge, 2014], 265) as follows:
1. Entities in all categories of being other than substance depend upon substance for their existence. 2. If (1), then if substances are perishable (as a class), entities in all other categories of being must also be perishable.
3. Hence, if substances are perishable, then time, which is in the category of quantity, can perish. 4. If time can perish, then time can also come into being.
5. If time can come into being and perish, then it is possible that there was a time before time.
6. That is absurd.
7. Hence, time cannot come into being and perish (4, 5, 6).
8. Time can come into being and perish if and only if change can come into being and perish. 9. Hence, change cannot come into being and perish (7, 8).
10. Hence, there always was and always will be change.
↩︎ - However, one can accept Aristotle’s general argument from motion for God without accepting the perpetuity of motion. Aquinas, for instance, does so. He thinks that it is not possible to philosophically demonstrate that the world has always existed (ST I, 46, I; see also: De aeternitate). He also thinks it is impossible to prove that the world had a beginning; for him, such a conviction is a matter of faith, not natural reason: “that the world began to exist is an object of faith, but not of demonstration or science” (ST I, 42, 2, co.). Nonetheless, he accepts the rest of Aristotle’s argument for a first cause of motion and presents his own condensed version of the Aristotelian proof for an unmoved mover in the first of the five ways (ST I, 2, 3, co.). He also develops the same argument at greater length in book I, chapter 13 of the Summa Contra Gentiles. ↩︎
- Physics 201a10-12. ↩︎
- Physics 251a9. ↩︎
- Because act and potency are the most basic explanatory principles, they cannot be defined in yet more basic terms. Thus, act and potency must be conceptually grasped by way of analogies: “What we wish to say is clear from the particular cases by induction, and we must not look for a definition for everything, but be able to comprehend the analogy, namely, that as what is building is in relation to what is capable of building, and what is awake in relation to what is asleep, and what is seeing is in relation to what has its eyes closed but has sight, and what has been shaped out of the matter is in relation to the matter, and what has been finished off is to the unfinished. Of the difference exemplified in this analogy let the actuality be marked off by the first part, the potentiality by the second” (Metaphysics 1048a35-b6). ↩︎
- “The same thing, if it is of a certain kind, can be both potential and fully real [i.e. actual], not indeed at the same time or not in the same respect, but e. g. potentially hot and actually cold” (Physics 201a19–22). ↩︎
- Physics 254b6-15. Here, Aristotle distinguishes between per se motion and per accidens motion and then makes various distinctions within each, the most important being between violent and natural motion. ↩︎
- Physics 254b24-33. ↩︎
- Physics 256b34-257a3, 257b6-258a21. ↩︎
- Physics 254b-33. ↩︎
- On the one hand, X is potentially F if it can acquire the property F; but in another sense, X is potentially F if it is F but not exercising the property F. Aristotle uses the examples of a learner who is potentially a knower and a man who has knowledge but is not exercising it (Physics 255a30-b5). The same is true of certain natural things: the heavy is potentially light in the first sense, whereas the light which is in the lower regions is potentially light in the second sense (255b5-13). The question may be asked why light and heavy things move to their own region, and the answer can only be that this is their nature (255b13-24). But, keeping in mind the distinctions between different senses of potency, we can say that, in reference to the first sense of potency, whatever makes something to be light or heavy is its mover; in reference to the second sense, whatever removes an obstacle to its motion activities the higher potency of a light thing and is therefore its mover, even if per accidens (255b24-256a3). ↩︎
- Physics 256a17-19: “…it is impossible that there should be an infinite series of movers, each of which is itself moved by something else, since in an infinite series there is no first term.” ↩︎
- Physics 256a5-8: “Further, in the latter case, either the mover immediately precedes the last thing in the series, or there may be one or more intermediate links: e.g. the stick moves the stone and is moved by the hand, which again is moved by the man.” ↩︎
- Physics 256a8-13: “Now we say that the thing is moved both by the last and by the first mover in the series, but more strictly by the first, since the first mover moves the last, whereas the last does not move the first, and the first will move the thing without the last, but the last will not move it without the first: e.g. the stick will not move anything unless it is itself moved by the man.” ↩︎
- Physics 256a21-256ab3. ↩︎
- Aristotle’s argument for the immovability of the first mover draws from his analysis of self-motion and terminates in the conclusion that the original mover of any motion must be unmoved. He insists that a self mover only moves itself by virtue of one of its parts being a mover and another part being moved: “when a thing moves itself it is one part of it that is the mover and another part that is moved” (Physics 257b12-13). This has to be the case for two reasons. First, something cannot move itself at all points or else it would be causing and suffering the same change as a whole. Secondly, that which causes motion must have something in act and that which is movable must be in potency, not yet possessing a particular actuality. But if something causes and suffers motion as a whole it would have to be in act and potency in the same respect at the same i.e. it would have to, for instance, be simultaneously hot and not hot. Thus, there must be a part of a self-mover that moves and a part that is moved (257a33-257b13). The original mover of any motion is therefore unmoved: “From what has been said, then, it is evident that that which primarily imparts motion is unmoved: for, whether the series is closed at once by that which is in motion but moved by something else deriving its motion directly from the first unmoved, or whether the motion is derived from what is in motion but moves itself and stops its own motion, on both suppositions we havethe result that in all cases of things being in motion that which primarily imparts motion is unmoved” (258b4-9). ↩︎
- Physics 258b10-259a19. ↩︎
- Physics 259a6-19. ↩︎
- “Now that these points are settled, it is clear that the first unmoved mover cannot have any magnitude. For if it has magnitude, this must either be a finite or an infinite magnitude. Now we have already proved in our course on Physics that there cannot be an infinite magnitude: and we have now proved that it is impossible for a finite magnitude to have an infinite force, and also that it is impossible for a thing to be moved by a finite magnitude during an infinite time. But the first mover causes a motion that is eternal and does cause it during an infinite time. It is clear, therefore, that the first mover is indivisible and is without parts and without magnitude” (Physics 267b18-26). ↩︎
- Metaphysics 1026a10-32. ↩︎
- Metaphysics 1003a33-b22. Also: APo 92b14; Top. 121a16-19. ↩︎
- Some commentators have understood this claim to mean that if immaterial substance didn’t exist, then metaphysics would not be its own science but would collapse into the philosophy of nature. That is, if physics was first philosophy it would include metaphysics within it. But Aristotle says nothing of the sort; all he states is that if immovable being didn’t exist, then physics (as presently constituted) would be first philosophy. That this seems absurd seems to the point Aristotle is trying make; impossibilities follow from denying the existence of immovable being: “We should, I believe, understand the ambiguous sentence as claiming that if immovable substance does not exist, then per impossibile the first science would be the science of the movable (of course), and there would be no separate science of being qua being. One does not have to show how physics could be that science, since this is an impossibility. That is, showing that physics is or contains the science of being qua being involves showing something that would follow from the opposite of a necessary truth—namely, a necessary falsehood. Nothing can or needs to be shown in this way. The intuitive plausibility of supposing that if the only things that exist are movables, there could naturally be as science of their being as opposed to as science of their being as opposed to a science of their movability is illusory” (Lloyd P. Gerson, Aristotle and Other Platonists [Ithaca/London: Cornell University Press, 2005], 177). ↩︎
- Metaphysics 1028a27-29. ↩︎
- Metaphysics 1028a33-35. ↩︎
- Metaphysics 1028a29-30. ↩︎
- Metaphysics 1028a37-1028b1. ↩︎
- Metaphysics 1028a35-36. ↩︎
- Metaphysics 1028b2-7. ↩︎
- Metaphysics 1003a33-1003b19. Quotation excerpted from: Christopher Shields, Aristotle, 2nd ed. (London/New York: Routledge, 2014), 281, 283-4. ↩︎
- Metaphysics 1005a13-18. ↩︎
- Metaphysics 1049b11-12; 1050a5; 1050b3; 1050b7ff. ↩︎
- See: Metaphysics VII, 17. See also: Frederick Copleston, A History of Philosophy Vol. 1: Greece and Rome (London/Oxford: Bloomsbury Continuum, 1946 ), 305-306. ↩︎
- Metaphysics 1071b12-22. ↩︎
- Metaphysics 1027b13. It is clear from these considerations that, owing to the priority of act over potency, the first principle of substances i.e. the primary substance must be essentially actual. But the question remains as to how exactly one should characterize the pure actuality of God. Aristotle thinks that, since intelligible substance is prior to sensible substance, the actuality in question must be a pure act of eternal thinking. Because thought is the noblest element of reality, and is therefore the most exalted aspect of being, God—the first principle of all beings who is in essence actuality—must be self-subsistent thought thinking itself (1072b13-30). ↩︎
- Metaphysics 1075a11. ↩︎
- Metaphysics 1072b3-4. When Aristotle inquires into how many movers are needed to account for the movements of the celestial bodies, he initially suggests that there are forty nine (1074a16). But since these forty nine are coordinated to form an orderly system, he thinks it necessary to postulate a single primary mover of them all such that, taken together, they constitute a single heaven: “That there is but one heaven is evident. For if there are any, as there are many humans, the starting-point for each will be one in form but many in number. But all things that are many in number have matter, for one and the same account applies to many, for example, humans, whereas Socrates is one. But the primary essence does not have matter; for it is an actuality. The primary immovable mover, therefore, is one both in account and in number. And so, therefore, is what is moved always and continuously. Therefore, there is only one heaven” (1074a31-38, excerpted from C. D. C. Reeve, Aristotle’s Theology: The Primary Texts [Indianapolis/Cambridge: Hackett Publishing Inc., 2022], xxvi). The argument given here is strange, however, in that it appeals to matter as the principle of individuation and argues that upon this basis that the immaterial primary mover is unique. But it is hard to see how, if this is the case i.e. if immateriality is what makes the primary mover one in number, there can be a plurality of immaterial movers at all. The relation of the plurality of movers to the first mover is left unclear and the problem of how there can be a multitude of individuated immaterial substances is left unresolved. Regardless, Aristotle’s central point here is that the unity of the heaven is accounted for by a single first cause. ↩︎
- The dependence of the reproductive cycles of living beings on the cycle of the seasons—in turn dependent on the motion of the sun, moon, and stars—is, for Aristotle, the most obvious indication of the unity of the sublunary and superlunary realms: “The cause of a human is both his elements, fire and earth as matter and the special form, and furthermore some other external thing, such as the father, and beyond these the sun and its movement in an inclined circle” (Metaphysics 1071a13-16, Reeve’s translation). ↩︎
- Metaphysics 1075a16-25. ↩︎
- Metaphysics 1075a13-1076a4. ↩︎
