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that God exists. If that is not achieved, all consideration of matters having to do with God (de rebus divinis) is nullified' (9.58).
But this is too stringent. Aquinas here is following Aristotle's line regarding the need to establish the existence of the subject of a particular science (organized body of knowledge) before undertaking the development of that
4 See Posterior Analytics I 1, 71al-b8; also Aquinas's commentary: In PA I: L2.14, 15, 18.
And the science he has in view here is, of course, only natural, and not also
5 For that reason an acceptable argument for the existence of God is essential to SCG as it isn't to ST, an introductory textbook of revealed theology. Theoretically, the inclusion of the famous Five Ways near the beginning of ST should constitute a digression from the project Aquinas is undertaking there.
But establishing God's existence is clearly not logically prior to 'a// consideration of matters having to do with God'. If it were, the classical argument from evil could be thrown out on a technicality, since it depends on understanding that any being that could count as God would have to be omnipotent, omniscient, and perfectly good. What's more, any'consideration by which it is demonstrated that God exists' must, similarly, presuppose an understanding of what could count as God, arrived at on the basis of some 'consideration of matters having to do with God'. I think we'll see that in Aquinas's own systematic natural theology acceptance of'God exists' isn't really an all-or-nothing propositional attitude that depends solely on some argument or arguments offered at the outset. 'The necessary foundation of the whole undertaking' does have to include evidence of God's existence strong enough to make that proposition attractive as a working hypothesis, to make it intellectually worth one's while to engage in a philosophical investigation of'God considered in himself'. But one's acceptance of the proposition 'God exists' can and should be allowed to develop on the basis of progress made in that whole undertaking.
On the way to arguing (in chapter 13) that God exists, Aquinas presents and rejects two quite different positions that are implicitly or explicitly in opposition to arguing for the existence of God as he proposes to do. In presenting and rejecting them (in chapters 10-12), he provides us with a clearer view of the sort of evidence he's committing himself to provide.
In the first place, he says (10.59-60), some of his predecessors end p.56
and contemporaries reject out of hand the project of demonstrating God's existence just because the unimpeachable certainty attaching to the proposition 'God exists' puts it at the level of propositions used as first principles of Aristotelian demonstrations, on a par with 'Every whole is greater than any one of its parts'. A proposition of that sort is 'known per se', recognized to be true as soon as its terms are fully understood; and its contradictory or contrary is inconceivable. Such a first principle, far from needing to be demonstrated, simply cannot be demonstrated, because there is no more fundamental proposition from which to derive it.
Two of Aquinas's five illustrations of this radical position regarding 'God exists' are the two ontological arguments from Anselm's Proslogion. That's odd, because, of course, Anselm is there arguing for 'God exists', and so may
seem not to be taking it as known perse.
6 Of course, a proposition may be self-evidently true and thus known (or knowable) per se even though not as far as we are concerned (quoad nos)—e.g. 'Goldbach's conjecture', the proposition that every even number larger than 2 is the sum of two prime numbers, which has until now been massively confirmed but neither proved nor shown to be undecidable. And although all arithmetical truths are knowable per se, many even mildly complicated propositions of that sort are not known perse at least as far as many of us are concerned, at least initially—e.g. 9,077/16 = 567.3125. Of course, in many such cases demonstrating the proposition's self-evident truth is something we can and should do. Might Anselm have been taking 'God exists' to be a proposition of that sort? In any event, Aquinas appears to be taking 'known per se' as equivalent to 'indemonstrable', which raises the possibility that he may be making only a technical point, tacitly acknowledging the possibility of a priori expository arguments for propositions known per se.
In fact, Aquinas recognizes Anselm's arguments as arguments, and provides particular objections to both of them. His reason for taking them as illustrations of this position emerges in his general account of the trouble with any approach that takes knowledge of God's existence to be derivable from putatively perse knowledge of God's nature. He thinks that such an approach assumes a level of understanding that is theoretically unattainable by philosophers or theologians—a level at which it would be clear perse to natural reason precisely how God's nature entails, or simply is, God's existence. People attracted by such arguments, he says, 'do not distinguish between what is known perse considered on its own (simpliciter) and what is known perse as far as we are concerned (quoad nos). Of course, that God exists is known perse considered on its own, since the very thing that God is
is his existence.
7 In this sentence Aquinas takes for granted the very difficult proposition that 'the very thing that God is is his existence', but only for the sake of relevantly invoking the distinction between propositions known perse considered on their own and propositions known perse as far as we are concerned. He will provide reasons for considering that proposition to be true (see Ch. Four), but at this point he's not even proposing it. It will not become part of his natural theology until he has argued for it, just because he (very plausibly) maintains that it can't be known perse as far as we are concerned.
But end p.57
because our minds cannot conceive of the very thing that God is, [his existence] remains unknown [perse] as far as we are concerned' (11.66).
Now this general indictment, too, may seem to miss Anselm by a mile. After all, the Anselmian formula identifying God as 'that than which nothing greater can be conceived of'—the formula on which the ontological arguments depend—is especially ingenious just because it seems to obviate any need to have a detailed conception of the very thing that God is in order 8
to argue that God exists.
8 It seems that the Anselmian formula's way of avoiding commitment to a detailed conception should have had special appeal for Aquinas, who maintains a little further on in SCG I that 'the divine substance is beyond every form our intellect acquires, and so we cannot apprehend it itself by discerning what it is' (14.117). Furthermore, the eliminative method he adopts when he begins his investigation of God's nature would seem to countenance the formula. (These moves on Aquinas's part are discussed in their own right in Ch. Three.)
However, a careful analysis of those arguments of Anselm's, and especially of the more formidable modal version in Proslogion 3, shows that Aquinas is right to find this difficulty even in those arguments. In assessing them, the crucial question turns out to be whether the conception of God in the Anselmian formula is internally consistent, and that question can't be answered definitively if we cannot penetrate beneath the formula to assess all the details of that conception, if we 'cannot conceive of the very thing that
9 For an astute analysis and appraisal of Aquinas's criticism of the ontological arguments, see Matthews 1963. Matthews shows that Aquinas's treatment of the arguments in SCG is more effective than the better-known one in ST. For some explanation of the apparent vagueness of Aquinas's treatment of Anselm's arguments, see Davies 1992: 24 n. 17.
But whatever we may think of Anselm's arguments or of Aquinas's treatment of them, the view that God's existence is known perse to human beings is bound to strike us, at the end of the twentieth century, as a most unlikely basis for objecting to Aquinas's procedure in SCG. Nobody we know is going to object to natural theology on those grounds. The second position Aquinas repudiates is one we're more likely to come across. 'Other people', end p.58
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© Copyright Oxford University Press, 2006. All Rights Reserved he says, 'have a view contrary to the position we have just been discussing, a view on the basis of which the effort of those who set out to prove that God exists would also be rendered useless. For these people say that God's existence cannot be discovered through reason, that it has, instead, been
accepted by way of faith and revelation alone' (12.72).
10 The statement of this position is implausibly weak. It seems that 'must ... be accepted' (est accipiendum) ought to replace 'has . . . been accepted' (est acceptum).
We in our day find that those who raise this objection to natural theology are motivated in one of two ways (and so did Aquinas in the thirteenth century). There are of course theists who are principled anti-intellectuals—those who would reject the very idea of natural theology as sacrilegious. The Christians among them sometimes share Tertullian's view—'After Christ Jesus, we have
no need of curiosity; after the Gospel, no need of inquiry'
11 De praescriptione haereticorum vii 12. See Kretzmann 1990.
—taking their cue, perhaps, from St Paul's warning against being made foolish by philosophy (Colossians 2: 8). But, as Aquinas observes, there are others who 'have been moved to say this because of the weakness of the arguments that some people have presented to prove that God exists' (12.73). And these others, or at least their twentieth-century intellectual descendants, will, of course, include many who deny the proposition that God exists while disdainfully relegating it to unquestioning acceptance by way of faith alone.
In Aquinas's general rejoinder to this objection, the Christian anti-intellectuals who shun his approach are reminded of what they are religiously bound to consider as 'the truth in the Apostle's saying in Romans 1[: 20] that the invisible things of God are clearly seen, having been understood through things that were made' (12.77). Proceeding along the lines of that Pauline observation in support of natural theology turns out also to be perfectly suited to the development of an Aristotelian science as Aquinas conceives of it. It depends for its starting-points on 12
12 See Posterior Analytics I 18, 81b2-9.
but 'teaches us how to draw conclusions about causes on the basis of their effects' (12.77). Thus, 'even though God transcends all sense-perceptible things and sense-perception, his effects, from which one draws a
demonstration to prove that God exists, are sense-perceptible' (12.80).
13 Here again it may seem that Aquinas is helping himself to an assumption he has no right to make. But these claims about God's transcendence of sense-perceptible things of which God is the cause are introduced here as part of Aquinas's development of Rom. 1: 20 only in answer to a religious objection to his project, not as part of his natural theology. His a posteriori arguments for God's existence will certainly not be taking it for granted that God causes sense-perceptible things or that he transcends them.
And so, as SCG's very many chapters on end p.59
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'God considered in himself' attest, Aquinas clearly does think that we are capable of reliably inferring a great deal about the nature and existence of God, that God's existence need not be 'accepted by way of faith and revelation alone', but can also be 'discovered through reason'.
What Aquinas leads us to expect in chapter 13, then, is an a posteriori demonstration of God's existence in which he will argue that sense-perceptible things, events, or states of affairs cannot be satisfactorily explained otherwise than on the basis of the existence of a being that is
plausibly identifiable as God.
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