Denys Turner identifies what he labels an “Augustinian principle” governing Milbank’s reading of St. Thomas-a principle that Turner believes leads Milbank astray in his interpretation of Aquinas’ five ways. According to Turner, Milbank sees the Summa Theologiae as reflecting Thomas’ shift to a more mature theological strategy in comparison to the more overtly philosophical approach of the Summa Contra Gentiles. In the Summa Theologiae, Milbank discerns a reconfigured relation between philosophy and sacra doctrina that involves a more away from an Aristotelian to a more Augustinian strategy. Thus, according to Milbank, in 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.” Turner then spells out what he discerns as Milbank’s Augustinian and ultimately Platonic hermeneutical principle with regard to Thomas, as well as the some of the implications of Milbank’s interpretation in relation to Thomas’s, as it were, “argument” strategy in the five ways.
If we are to know the most perfect good ‘to be’, there must exist, prior to any theological expansion of the radical unknowableness of God into an account of the divine attributes, ‘a certain preontological 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’ [Milbank, "Intensities," p. 455]. 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 it 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. 459-460].
In light of the fact that if this read is correct, it would seem to make Thomas guilty of a rather elementary logical error, viz., the fallacy of petitio principii, Milbank opts for the conclusion that Thomas was not presenting his arguments in the five ways as formally valid proofs for God’s existence.
Turner, not surprisingly, thinks that Milbank’s reading of Thomas is seriously flawed. First of all, Turner directs us to Thomas’ fourth way and emphasizes that Thomas did not claim that we have knowledge of degrees of goodness in finite things only because we already possess knowledge of perfect goodness, viz., the goodness which is God. Turner also denies that Thomas, unlike Anselm, Bonaventure, Descartes and Augustine, holds the following proposition to be true: “we can perceive relative degrees of a quality only if we have prior knowledge of what would count as the maximal degree of it.” Rather, Thomas presents his fourth way as an attempt to argue for the existence of some maximal or supreme goodness because we meet with varying degrees of goodness in the things of our experience. According to Turner, even if one rejects the inferential validity of Thomas’ fourth way, “the argument is clearly presented as an inference, moreover to a cause, ‘which we call God.'” Secondly, Turner fundamentally disagrees with Milbank’s claim that to engage in natural theology, that is, to attempt to offer logically valid proofs for God’s existence necessarily involves one in some form of “Scotist onto-theology.” In fact, Turner’s main purpose in writing this book is to argue that “there are reasons of faith why in principle the existence of God should be thought rationally demonstrable and that it is worthwhile revisiting the theology of Thomas Aquinas to see why this is so.” Turner goes on to point out that Milbank misreads Thomas as claiming that inferential validity requires a univocity of terms. According to Turner, Milbank thus bases his claim of the impossibility of scientific demonstration of God’s existence on a Scotist principle that Thomas himself never accepted. Both Thomas and Scotus agreed that inferential validity rules out the use of equivocal terms, but Thomas did not conclude with Scotus that analogical terms could not yield a valid inference.
Turner closes the section with the claim that Milbank’s objection to logically valid proofs for the existence of God “appears to rest on the supposition that if transgeneric demonstration is invalid, then an inference which purported to transgress the boundary between any created genus and God, who is beyond every genus, must by at least the same token be invalid” (p. 201). This, however, according to Turner is a non sequitur. As Turner explains,
To suppose without more ado that because an inference is invalid by the fallacy of equivocation if it crosses from one genus to another it must be at least as invalid if it crosses from generic being to God, who is beyond every genus, is to suppose, without more ado, that the gap to be crossed between one genus and another and the gap to be crossed between generic being and God are logically the same kinds of gap, only-one supposes-‘bigger’ in the latter case (p. 201).
In other words, to assume that these gaps are logically the same kinds of gaps is to place God and creation on the same scale-it is just a bigger gap that must be crossed with regard to God and creation than the gap between one genus to another.
Turner then adds that this non sequitur is significant because it shows that Milbank’s critique is operating on a Scotist assumption. Neither Thomas nor Scotus nor Milbank hold that God belongs to a genus, yet, Turner says, “though Scotus, unlike Milbank and Thomas, so construes the ‘gap’ between God and creatures as to be logically of the same kind as that between one genus and another, Milbank, like Scotus and unlike Thomas, holds that inference could cross the gap between creatures and God only if that gap fell univocally within a common genus” (p. 201).
I see Turner’s point; however, I am still not completely convinced that Scotus is really guilty of viewing these “gaps” as being of the same logical status. After all, Scotus’ definition of the infinite is, “What I call ‘infinite’ is what excels any actual or possible finite being to a degree beyond any determinate measure you take or could take.” Couldn’t this be read as suggesting that for Scotus, the difference between God and creation is incommensurable?
 Milbank, “Intensitites,” Modern Theology 15.4, October 1999, p. 455, as quoted in Turner, Faith, Reason and the Existence of God, p. 196.  Turner, Faith, Reason and the Existence of God, p. 196.  Ibid., p. 198.  Ibid., p. 198.  This quote is taken from the opening page of the book which has no page number.  Wolter and Frank. Duns Scotus Metaphysician, p. 59. As found in Reportatio IA in the “reply to the third question”.