Chapter 3. Arguing for God’s Existence (SCG 1,13)
CHAPTER 3. ARGUING FOR GOD’S EXISTENCE (SCG 1,13)
1. ND, 1, 85 [1].
2. So Aquinas actually ends up delivering less in SCG 1,13 than he might seem to be promising. The opening words of SCG 1,13 might be taken as suggesting that Aquinas is about to engage in an extensive history and defense of proofs of God’s existence. But he does not do that. Why not? I suspect it is because he thinks that in SCG 1,13 he has said enough to demonstrate that God exists for his purposes at this stage of the SCG. In later chapters he has more to say when it comes to causal reasoning to the conclusion that God exists.
3. I am not concerned to enter into a discussion of whether or not Aquinas accurately represents Aristotle while drawing on him in SCG 1,13. I am not concerned to discuss the accuracy of Aquinas on Aristotle at any point in this book. My aim is to focus on what Aquinas thought Aristotle said and to follow him accordingly for purposes of expounding him. For an account of SCG 1,13 and Aristotle, see J. Owens, “Aquinas and the Proof from the Physics,” Medieval Studies (1966). The passage in Physics VII that Aquinas seems to have especially in mind in SCG 1,13 reads: “Everything that is in motion must be moved by something. For if it has not the source of its motion in itself it is evident that it is moved by something other than itself, for there must be something else that moves it. If on the other hand it has the source of motion in itself, let AB be taken to represent that which is in motion of itself and not in virtue of the fact that something belonging to it is in motion. Now in the first place to assume that AB, because it is in motion as a whole and is not moved by anything external to itself, is therefore moved by itself—this is just as if, supposing that KL is moving LM and is also itself in motion, we were to deny that KM is moved by anything on the ground that it is not evident which is the part that is moving it and which the part that is moved. In the second place that which is in motion without being moved by anything does not necessarily cease from its motion because something else is at rest; but a thing must be moved by something if the fact of something else having ceased from its motion caused it to be at rest. If this is accepted, everything that is in motion must be moved by something. For if AB is assumed to be in motion, it must be divisible, since everything that is in motion is divisible. Let it be divided, then, at C. Now if CB is not in motion, then AB will not be in motion; for if it is, it is clear that AC would be in motion while BC is at rest, and thus AB cannot be in motion in its own right and primarily. But ex hypothesi AB is in motion in its own right and primarily. Therefore if CB is not in motion AB will be at rest. But we have agreed that that which is at rest if something is not in motion must be moved by something. Consequently, everything that is in motion must be moved by something; for that which is in motion will always be divisible, and if a part of it is not in motion the whole must be at rest.” I quote from The Complete Works of Aristotle, edited by Jonathan Barnes (Princeton, NJ: Princeton University Press, 1984), 407–408.
4. It has been suggested that in SCG 1,13 Aquinas only argues that something moving is moved by another. Yet the best sense of what he says has him thinking that what is moved (passive) is moved by another, not that anything in process of movement is being moved by something else. See James E. Weisheipl, Nature and Motion in the Middle Ages (Washington, DC: Catholic University of America Press, 1985), 76–77. Aquinas takes “to be moved” as what Weisheipl calls “a passive capacity for someone else’s action.” He reasons that “someone else must do the acting.” As Weisheipl also says, “St. Thomas never said, Omne movens ab alio movetur [Everything moving/in process of motion is moved by another]” or that “everything that is in motion must be here and now moved by something” (78).
5. As should be clear, I am taking Aquinas’s word motus to be translatable into English as either “movement” or “change.” In what I go on to say about SCG 1,13, however, I shall largely stick with ND, 1’s use of “move,” “moved,” “motion,” and so on.
6. Some philosophers have argued that there is no world external to us considered as thinkers. If they are right, then we can regard most or all of the SCG to rest on a huge mistake. Since nobody acts on the assumption that the view I have just referred to is correct, I shall say nothing more about it in this book. Aquinas never discusses it in any of his writings. Perhaps the reason why is obvious. If you do not find it obvious, consider what you would be presupposing when trying to argue that there is no external world of which any of us have knowledge. For example, with what or whom would you take yourself to be arguing?
7. “Move” in English can be transitive or intransitive. I can move my cat or move out of my cat’s way. In Latin, the passive form of the transitive verb movere is used to express the intransitive sense of “move.” So “movetur” could equally mean “is moving/is in motion” or “is moved.”
8. ND, 1, 86 [5].
9. ND, 1, 86 [5].
10. ND, 1, 86 [5]. Aquinas goes on to note that Plato thought that something might move itself without being a bodily thing. How so? By understanding or judging itself. However, Aquinas is here thinking of what moves itself as being what he is arguing for in SCG 1,13, something “absolutely unmoved” in the sense of these words that Aquinas takes Aristotle to be working with. As I will show, Aquinas thinks that there can be movement of a sort even in what is wholly unmoved since he draws a distinction between acts (movements) that remain in one and others that go “out of one” so to speak. I can reflect on myself, this, for Aquinas, not being an action that goes outside me. Or I can kick my cat, this being an action that, for Aquinas, definitely goes outside me (because there is something other than me involved in it).
11. ND, 1, 87 [6]. I am assuming that Aquinas is here saying that, for example, if I can be said to be at rest because a part of myself is at rest (since my foot, say, is not moving), then I am at rest only because a part of me is and I am, therefore, not at rest “primarily” and of my own accord but only because a part of me is at rest. And I am assuming that Aquinas is taking this point to imply that nothing primarily moves itself if it is moved by a part of itself.
12. ND, 1, 87 [7].
13. See Aristotle, Physics 8(254b–257b). By “inductive” Aquinas means “based on empirical investigation.”
14. By “causes removing impediments” Aquinas is thinking, for example, of me permitting (and thereby causally accounting for) the water in my bath to flow away because I remove the bath plug.
15. ND, 1, 88 [9]. See Physics 8,5.
16. Anthony Kenny, The Five Ways (London: Routledge and Kegan Paul, 1969), 21.
17. See Summa Theologiae 1a,4,2. Here we read: “Any perfection found in an effect must also be found in the effective cause of that effect—either as it exists in the cause, when cause and effect are of the same sort (as when people beget people), or in a more perfect manner, when cause and effect are not of the same sort (as when the sun’s power produces things having a certain likeness to the sun).” I quote from Aquinas: “Summa Theologiae,” Questions on God, edited by Brian Davies and Brian Leftow (Cambridge: Cambridge University Press, 2006), 46.
18. John F. Wippel, The Metaphysical Thought of Thomas Aquinas (Washington, DC: Catholic University of America Press, 2000), 447. Wippel offers an analysis of texts of Aquinas on agent causation in “Thomas Aquinas on Our Knowledge of God and the Axiom that Every Agent Produces Something Like Itself,” which is chapter 6 of John Wippel, Metaphysical Themes in Thomas Aquinas II (Washington, DC: Catholic University of America Press, 2007).
19. ND, 1, 89 [12].
20. Aquinas did believe that the world had a beginning, but, he says, this is a conclusion that has to be arrived at by people on the basis of faith in what the Bible says. It is not demonstrable. See Summa Theologiae 1a,46 and SCG 2,38.
21. ND, 1, 90 [14].
22. ND, 1, 90 [15].
23. Aquinas’s “true by itself”/“true by accident” distinction amounts to the distinction between what is true of absolute necessity and what just happens to be true. If I am a human being, I am necessarily something with a body (the idea of having a body is built into our idea of being a human being). But if I am a human being, it is not necessary that I should have visited Hong Kong or have a tattoo of a penguin on my chest. If I have visited Hong Kong or have a tattoo of a penguin on my chest, that is just something that happens to be true of me though it might never have been true of me.
24. I take it that Aquinas would regard as “false and impossible” a proposition like “Some triangles have four sides.” And I take it that he would regard a proposition that is “possibly true but actually false” to be one such as “Brian Davies, the author of this book, has a tattoo of a penguin on his chest.” Some philosophers have claimed that what seems to be impossible cannot be captured in a genuine proposition. Others have said things to cast doubt on there being any genuine proposition captured by sentences with words like “this” in them (since “this,” to put it mildly, is a very vague word). Even if you accept these theses, however, you will surely see what Aquinas is saying at this point in the SCG.
25. By “accidental feature” Aquinas means one that something might have but does not have to have given what it is by nature. So, I might be musical, but the fact that I am a human being does not guarantee that I am musical. As well as being musical, I might also be bald, which I do not have to be just because I am human (there are plenty of nonbald people). Now suppose that I happen to be both bald and musical. Does it follow that I have to be both of these things? Apparently not. This is what Aquinas is saying at this point in the SCG.
26. The suggestion seems to be that, for example, though Fred, as it happens, is both musical and bald, it is probable that there is someone who is musical and not bald or that there is someone who is bald but not musical.
27. ND, 1, 91 [19]. Here Aquinas is alluding to the fact that things can undergo different kinds of changes in the ways I mentioned above: change of place, change of quality, and change of quantity. So, he is saying, for example, that something moving locally (change of place) is either moved by what itself moves locally or by something undergoing change of quality or quantity.
28. ND, 1, 91 [19].
29. ND, 1, 95 [32]. In the present paragraph my summary of what Aquinas is saying at this stage in SCG 1,13 omits some twists and turns that Aquinas presents in his text. But I think that it conveys the sense of what he is driving at. For a more complicated analysis, see Norman Kretzmann, The Metaphysics of Theism: Aquinas’s Natural Theology in “Summa Contra Gentiles” 1 (Oxford: Clarendon Press, 1997), 72–83. Also note Wippel, The Metaphysical Thought of Thomas Aquinas, 427–431.
30. This argument is often referred to as the Kalām Cosmological Argument. For a defense of it, see William Lane Craig, The Kalām Cosmological Argument (London: Macmillan, 1979). For criticisms of the argument, see J. L. Mackie, The Miracle of Theism (Oxford: Clarendon Press, 1982), 92–95. For discussion of the argument by me, see my An Introduction to the Philosophy of Religion, 3rd ed. (Oxford: Oxford University Press, 2004), 48–54.
31. ND, 1, 96 [35].
32. ND, 1, 96 [35].
33. Referring to a passage in the Summa Theologiae in which Aquinas speaks about degrees of truth, P. T. Geach interprets Aquinas to be holding, somewhat absurdly, that, for example, “if one lie is a bigger lie than another, the truth opposed to one is a bigger truth than the truth opposed to the other.” See G. E. M. Anscombe and P. T. Geach, Three Philosophers (Oxford: Blackwell, 1961), 116. I doubt that Geach is right here, but Aquinas’s talk about degrees of truth is somewhat obscure.
34. What might Aristotle have made of SCG 1,13 (read in the context of the SCG as a whole) had he been able to read it? I do not know since I am not an expert on Aristotle, though there are doubtless experts on Aristotle today who might venture some guesses.
35. Aquinas thinks that there are beings that are both necessary and created. I elaborate on this notion in chapter 10.
36. My quotations from the Summa Theologiae here come from Davies and Leftow, Aquinas: “Summa Theologiae,” 25–26.
37. Dictionaries are full of what Aquinas would have thought of as nominal definitions of nonexisting things. Think about dictionary definitions of words like “chimera,” “unicorn,” “fairy,” “elf,” and so on.
38. See Kenny, The Five Ways, 18–19: “If a thing cannot be moved by itself, it does not follow that it must be moved by something else. Why cannot it just be in motion, without being moved by anything, whether by itself or anything else?”
39. See Kenny, The Five Ways, 28: “At any given time, the rectilinear uniform motion of a body can be explained by the principle of inertia in terms of the body’s own previous motion without appeal to any other agent.” Newton himself actually said: “Every body perseveres in its state of rest or of uniform motion in a straight line, unless it is compelled to change that state by forces impressed on it” (Philosophiae Naturalis Principia Mathematica, bk. 1 [1687]).
40. See Kenny, The Five Ways, 26–27. Also see C. J. F. Williams, “Hic autem non est procedere in infinitum,” Mind 69 (1960). Williams suggests that Aquinas falls victim to fallaciously assuming that if something is a “secondary cause,” there has to be a first cause—the conclusion here assuming what has to be proved given its introduction of the phrase “secondary cause.” According to Williams, we are not entitled to claim to know that an infinite series of causes is impossible unless we first know that all movers are properly described either as first or second movers. Williams’s argument is directed against what Aquinas writes in Summa Theologiae 1a,2,3, but I suspect that he would have taken it to apply to what we find in SCG 1,13. Kenny, at any rate, seems to take it to do so.
41. See Kenny, The Five Ways, 23.
42. Among others, Scott MacDonald does this in “Aquinas’s Parasitic Cosmological Argument,” Medieval Philosophy and Theology 1 (1991).
43. The Metaphysical Thought of Thomas Aquinas, 454. For a more detailed defense of this point, see “The Specter of Motor Coniunctus,” which is chapter 5 of Weisheipl’s Nature and Motion in the Middle Ages.
44. Edward Feser, Aquinas: A Beginner’s Guide (London: Oneworld, 2009), 79.
45. Hume, A Treatise of Human Nature, bk. 1, sec. 3. For other relevant texts by Hume, see An Enquiry Concerning Human Understanding, secs. 4 and 5.
46. This is what Aquinas says in his commentary on Aristotle’s Physics. I quote from Thomas Aquinas: Selected Philosophical Writings, translated by Timothy McDermott (Oxford: Oxford University Press, 1993), 83 and 84.
47. See Summa Theologiae 1a,22,2, ad.1.
48. Aquinas, 76.