In a sub-section entitled, “Thomas and ‘onto-theology’”, of chapter nine of Denys Turner’s book, Faith, Reason and the Existence of God, Turner discusses possible ways that Thomas’ acceptance of a famous dictum by the Pseudo-Denys might be taken, and whether any of the interpretations can avoid falling into the error of onto-theology. According to the Denys, “There is no kind of thing that God is.” One way of interpreting this statement is that God’s existence is unspecified. This would then suggest that the name “God” means existence in general, that is, existence of no particular kind. As Turner explains, this reading might then be taken in two possible ways. The first way would land one in pantheism, as the name “God” would simply name the “overarching category of ‘being’ of which all other beings other than God are instances” (p. 187). In this picture, it follows that creatures are just instances of God; hence, onto-theology is unavoidable. The second possibility would likewise be guilty of onto-theology, as here both God and creatures are instantiations of being in general. Thomas, however, rejects these options and insists both that God is ipsum esse subsistens (and hence, not “any kind of thing”) and that this does not mean that the name “God” points us to an “empty category.” Rather, as Turner puts it,
[t]hat we cannot form any ‘concept’ of God is due not to the divine vacuousness, but, on the contrary, to the excessiveness of the divine plenitude. That excessiveness eludes our language because we could not comprehend it except in a surplus description which utterly defeats our powers of unification under any conception, an excessiveness which is exactly captured in the full text of the Dionysian formula, ‘There is no kind of thing which God is, and there is no kind of thing which God is not.’ If ever there were a compendious statement of the relationship between the apophatic and the cataphatic in the pseudo-Deny’s writing, this is it: for it says that God is beyond our comprehension not because we cannot say anything about God, but because we are compelled to say too much. In short, for the pseudo-Denys, and for Thomas following him, the ‘apophatic’ consists in the excessus of the ‘cataphatic’ (pp. 187-188).