The logic of proof

In this chapter, therefore, we are first brought to the question of the logic of proof. In a recent article, Milbank writes of how there is in Thomas's Summa Theologiae 'a much more integral relation between sacred theology and metaphysics'1 than there is in his earlier Summa contra Gentiles. In the earlier Summa, the overall structure and balance indicate just how much room Thomas was at that stage of the development of his theology prepared to allow for natural reason within the articulation of his theology, for three out of four parts of this vast work could be said to rely upon philosophical arguments principally or alone, and only in the final part is any explicit reliance on the authority of faith appealed to. This is so, the fact notwithstanding that in the first three 'philosophical' parts of his work, scriptural and other Christian authorities are frequently invoked; for such appeals appear but to serve a purpose of reassurance for Thomas's Christian readers that his philosophical arguments in no way lead him astray from central Christian teachings and theological traditions. Moreover, there appears to be an apologetic purpose of the Summa contra Gentiles - thought by Milbank to account for the prominence given to metaphysics which Thomas did not elsewhere accord to it. But the fact of an apologetic purpose, if such it be, cuts both ways. For it

1 John Milbank, 'Intensities', Modern Theology 15.4, October 1999, pp. 445-97.

would be no compliment to Thomas's good theological faith to suppose that he would have adopted the theological strategies of the Summa contra Gentiles as an apologetic tactic had he thought that to do so would be in any fundamental way inappropriate and distorting of good theological method. It seems that Thomas was prepared to employ a wide variety of expository methods, adapted to different purposes - as is shown by his having adopted a third, quite different expository scheme in his last, and again incomplete, work, the Compendium Theologiae.2 Thomas, at least, appears to have attached little systematic significance to different strategies and 'mixes' of metaphysics and revealed theology, preferring, it seems, to fit horses to courses.

Milbank, however, sees the structural differences between the heavily metaphysical Summa contra Gentiles and the much lighter philosophical emphases of the Summa Theologiae as indicating a significant conversion to a maturer theological strategy. In the later Summa, he says, 'the "preliminary" role of metaphysics on its own as establishing God as first cause is now barely gestured towards, and instead the focus is upon the need of sacra doctrina itself to deploy philosophical arguments' ('Intensities', p. 454) within and for strictly theological purposes and not on account of any claim for an 'autonomous reason'. Thus far this is more or less exactly what I argued in chapter 2 about the structure of the first twenty-six questions of the Summa Theologiae. Moreover, in agreement not only with Thomas, but also (as it happens) with the propositions of the first Vatican Council, Milbank adds that the recourse of sacra doctrina to philosophical arguments is not necessitated by any 'innate deficiency' on the part of sacra doctrina in comparison with what it 'borrows' from philosophy - as if the transition from rational argument to theological faith were a transition from philosophically guaranteed certainties to a faith 'clinging to uncertainties' (ibid.). For on the contrary, the reconceived relation between philosophical argument and sacra doctrina found in the Summa Theologiae now ensures that 'one passes imperceptibly from the relatively discursive to the relatively intuitive as one more nearly approaches the pure divine insight' (ibid.). Therefore, rather than being necessitated on account of theology's deficiency, Milbank argues,

[sacra doctrina's recourse to discursive reason] is necessary on account of the innate deficiency of human reason, which cannot, short of the final vision of glory, grasp what is in itself most intelligible, but must explicate this in terms of reasons clearer to humanity, but in themselves less clear, which is to say, less rational. (Ibid., emphasis original)

2 The structure of the Compendium is organised around the three 'theological' virtues of faith, hope and charity. The work is left incomplete in mid-course of the discussion of hope.

It is, Milbank thinks, at the heart of this reconceived relation between philosophy and sacra doctrina that Thomas moves away from a more 'Aristotelian' and pagan-rationalist formula to a more openly Augustinian position; within the Summa Theologiae 'a posteriori demonstration from creatures plays a weak role ... and there is in fact much more Augustinian a priori (so to speak) argument - in terms of "what must" belong to perfection - than is usually allowed' (ibid., p. 455).3 And it is in this connection that the dominating Augustinian - and ultimately Platonic -principle governing Milbank's reading of Thomas becomes most explicitly acknowledged. If we are to know the most perfect good 'to be', there must exist, prior to any theological expansion of the radical unknow-ableness of God into an account of the divine attributes, 'a certain pre-ontological insistence of the ideal', so that we can respond to it; respond, that is, to 'an as it were a priori vision of the good' (ibid.). But since Thomas explicitly prohibits any a priori philosophical theology which, in the manner of Anselm's Proslogion argument, would purport to prove the necessary existence of the highest perfection from that perfection's being the highest, there is no argument which by itself can get you to that a priori vision - indeed, it could not have the character of the a priori if it was argument from creatures which got you there - and so 'the only thing that authenticates perfection must be some sort of experience of its actuality' (ibid., p. 456). Moreover, such an experience of'highest perfection' must be presupposed even to Thomas's a posteriori proofs of the existence of God (ibid., pp. 459-60). Why so?

For these reasons, Aquinas' argument for a first mover (the 'first way') has validity, Milbank thinks, only because the starting point, or premise, motion, 'is understood from the outset as being undergone with a purpose, or for a reason, and on account of a goal in accord with nature' (ibid.); hence, all motions, being 'aims towards perfections', are knowable in that ontological dependence on their first cause in which demonstration of God would consist, only in so far as the perfections aimed at are already known in their participations 'of the supreme end, the supreme good'. Hence, 'the first mover is really radically presupposed' to the premise from which the arguments proceed (ibid.). Fergus Kerr argues to a similar end as regards the logic of proof when he notes that if Thomas's arguments for God proceed, as Thomas says they do, from the divine effects to God as their cause,4 then one has to doubt whether he can be regarding them as formally valid proofs at all: for one is constrained to ask, 'Why should

3 Milbank, 'Intensities', p. 455. Milbank does not explain on what standards of strength and weakness the 'strength' of the role of a posteriori arguments in the second question of the Summa is here being assessed.

4 Thomas Aquinas, Summa contra Gentiles 1, 12, Opera Omnia 14, Leonine: Rome, 1926.

we regard features of the world as "effects"? Is that not what argument for the existence of God is supposed to achieve - to demonstrate, philosophically, that things are "caused" in such a way that they may be called "effects", thus of some "cause"?'5 Hence, an argument which works up to God by inference from 'effects' must presuppose the existence of God in the very characterisation of its premises as 'effects'. Of course, as we saw earlier, it would follow from either account that, considered as formal demonstrations, the five ways would be simply invalid, since they would fail by the fallacy of petitio principii. For while they would appear to be proving a conclusion, they would in fact presuppose that conclusion at least implicitly as a premise.6 For which reason Milbank and Kerr (one imagines supposing Thomas to be incapable of such elementary failures of logic) charitably read them as not being intended as formally valid proofs of the existence of God.

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