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Monday, December 10, 2012

0255: John Haldane on Aquinas (I)

Entry 0255: John Haldane on Aquinas (I)

In a recent interview, Professor John Haldane was asked: “Aquinas’ famous cosmological argument is partly famous because it has been subjected to huge critical study and would seem to have been rendered obsolete. Haven’t developments in modern logic after Frege left much of Aquinas generally in a mess? Doesn’t too much of the original system – brilliant though it was in the time he was writing – depend on errors that subsequent generations have discovered?”

Professor Haldane answered: “There are several places in Aquinas’ writings where he refers to natural philosophy, i.e. to what we would consider empirical science, and makes statements that we now know to be false. Examples concern human physiology, conception and embryological development, and aspects of physics, chemistry and astronomy. Where these are invoked in arguments, e.g. about sensation, the beginnings of life, or the nature of the heavenly bodies the result may be to render arguments unsound, but the deeper issues are generally metaphysical and the interesting question is whether the arguments can be reformulated in terms of corrected empirical facts, and how far such reformulation takes one away from Aquinas’ central purpose.

“So far as arguing to the existence of God is concerned, Aquinas’ main lines of argument do not depend essentially on particular empirical theories. These are set out in the ‘Five Ways’ presented in the second question of his major work the Summa Theologiae, but there are other arguments elsewhere.

“Let me mention two lines of reasoning one teleological, the other cosmological.

“Aquinas claims that the action of some natural organisms is explicable in terms of the ends towards which they move, even though they lack intelligence. These ends generally confer benefits relevant to the natures of the organisms and hence conduce to their good. If we thought of these agents as choosing the ends then we might think that no further explanation was called for, but if they are incapable of choice then there must be some other explanation of their tendencies towards beneficial states, something external and directional, and from this Aquinas reasons to the idea of a benign designer, saying that this is what we call God (‘et hoc dicimus Deum’).

“There is much that has been said about this kind of argument and it is commonly supposed to have been defeated by the theory of evolution through mutation and natural selection. But evolutionary speciation itself rests on teleologically-structured processes which it does not and cannot explain. There is much more to be said and if readers want to see how this debate might develop they could look at my debate with the late Jack Smart in Atheism and Theism. Here all I want to point out is that the argument neither excludes nor is rendered unsound by evolutionary processes.

“The second argument is that involving essence and existence – and by existence I mean actuality or ‘be-ing’, i.e. existing. In this sense existence is a metaphysical aspect of any existing thing and it is not captured by the existential quantifier.

“Aquinas points out that if we were to inquire into some kind of entity we might ask what is it? i.e. ask about its nature or essence, but also ask is it? does it actually exist? The fact that the second question remains open even when the first has been answered shows that the existence of the thing does not follow from its essence. So if it exists its existence must derive from something else.

“Of that prior source one can again ask whether its existence is implied by its nature and if not then we have to look for a further source, and so it continues. If a vicious regress is to be avoided we must suppose that there is something in which existence is implied by essence and which has the power to confer existence on other things. So again Aquinas is led to the idea of God as the creator, and indeed sustainer of the being as well as of the natures of beings. While this argument may be contested it is a purely metaphysical one and does not rest on particular empirical claims and hence is not refutable by appeal to scientific discoveries.”

The interview was first published by “3:AM Magazine” on Tuesday, 4 December 2012 under the title “Aquinas amongst the Analytics.”

Link to the full interview: