Appendix 20.

(621) [St. Thomas on substance]

St. Thomas deduces the idea of substance in the same way as I do. First, he establishes that the proper object of the intellect is ens or common truth (objectum intellectus est ens, vel verum commune). He concludes that everything is knowable in so far as it is, in so far as it has an existence of its own. This is my conclusion also. It is in fact absurd that what is not, could be understood: Unumquodque autem in quantum habet DE ESSE* , in tantum est cognoscibile [Each thing is knowable in so far as it has wherewith TO BE] (S.T., I, q. 16, art. 3). It follows that things are understood through their substance because substance is that by which they are entia. This accounts for St. Thomas' other declaration where he states that substance is the object of the intellect precisely because the object of the intellect is ens: Quidditas rei est proprium objectum intellectus [The proper object of the intellect is what makes a thing what it is] (S.T., I, q. 85, art. 5). Another acute observation, drawn from this very principle, is that the truth in things is their substance and their very being: Verum autem quod est in rebus, convertitur cum ente secundum substantiam [What is true in things is interchanged with being in the realm of substance] (S.T., I, q. 16, art 3). The truth of things is their relationship with ideas in the intellect, which however can only be of their substance, because this is the object of the intellect. It follows that truth, in so far as it is shared by things, is their substance. Note that quidditas, in the quotation above, has been equated with substance because of the meaning given it by St. Thomas in this place; it is always true that the quiddity or essence of accidents can only be understood related to substantial quiddity or essence.