Aquinas on Simplicity: an Investigation into the Foundations of his Philosophical Theology. By Peter Weigel


Pp. 265 , Oxford, Bern , Peter Lang , 2008 , $62.00 .

Simplicity safeguards and negatively constitutes the extreme transcendence of the monotheistic deity of the Abrahamic religions. Distinctive in elevating their God up and out of the world, of which he is no part but creates by a free act of the will, this doctrine draws further cultural support from Greek philosophy where Plato described his ‘Form of the Good’ as ‘beyond Being’ (where ‘Being’ indicates the immutable, static existence of the Forms) and Aristotle described his Unmoved Mover, who draws all things by attraction, himself unmoved, as ‘Pure Act’. Aquinas seems to have grown in his appreciation of how unique and central this property is. In his early Summa contra Gentiles and Compendium theologiae the prominence of simplicity is less marked; Thomas felt the need to do systematic theology all over again, however, and in his magisterial Summa theologiae simplicity moves to become the foundational predicate of the divine nature, from which the other predicates variously derive. This follows an historical pattern; neither Plato nor Aristotle ever called their highest principle ‘infinite’; this was left to Plotinus, who wanted to lift his ‘One’ into a further transcendence and who made simplicity into not only the first divine predicate, but also the most appropriate name for God – above ‘Form’ for Plato and ‘Substance’ or ‘Being’ for Aristotle. This was done to highlight the chief element in God's transcendence – his lack of composition, which entails his lack of motion or capacity for further perfection. Henceforth theological speculation would walk a knife edge of trying to avoid a purely apophatic or negative theology on the one hand (which Maimonides fell into) or a pluralism in the divine attributes irreconcilable with the postulated divine simplicity (as with David Hume and his modern followers who refuse to recognize the super-eminent status which extreme transcendence grants such a being.)

Two doctrines allow Aquinas to walk this knife edge. First, the identification of existence and essence in God means that his essence, although unitary, remains sufficiently opaque or mysterious to us to provide a prophylactic against a premature dismissal of how plural but distinct perfections can be united in the divine essence, re-enforced by the doctrine that the ‘pure act’ of esse contains all perfections in super-eminent fashion. Secondly, the principle that there is a trace of the first cause in each of its effects provides a toe-hold for positive analogical predication about God, freed from the limiting circumstances in which such perfections appear among creatures.

Beyond that, Weigel shows how Thomas was correct to shift the primary or most appropriate name for God from simplicity (Plotinus) to Being, as superior at disclosing the nature of the divine reality – this despite the notorious complaints of its being ‘empty’ or ‘difficult to conceive’ filed by Kant and later moderns. First is what might be called Thomas' ‘modified occasionalism’: God does not cause all effects directly, but he does cause directly the existence of the agencies that produce these effects; and since we are investigating actual effects, an account of both must be given in a complete or adequate account (p. 122). Secondly, the very transparency or ‘being difficult to conceive’ of Being that works against it compared to the seeming precision offered by other perfections, turns to an advantage when we are fishing for a super-eminent term to capture the distinctive effect of the creator-God, who makes so many different kinds of things in so many modalities. As Weigel puts it: ‘Our terms signify the perfection as if it were limited to a determinate kind and degree, while God's power infinitely exceeds the sum of all perfections …‘Being’, like ‘actuality’, covers or expresses the ontological substratum of all perfection, but indeterminately so, without regard to kind or limit.’ (p. 207). And quoting Thomas: ‘(A)ll these names signify the divine substance, although not as comprehending it, but imperfectly: and for this the name ‘He Who Is’ is most becoming to God, since it does not ascribe any particular form to God, but signifies being without any limitation …He Who Is denotes a boundless sea of substance.’