Existential Propositions in the Thought of St. Thomas Aquinas

EXISTENTIAL PROPOSITIONS IN THE THOUGHT OF ST. THOMAS AQUINAS A REVALENT VIEW of St. Thomas Aquinas's position on the logic of propositions has been that according to him propositions of the :form, x is, hold a privileged place, that they are in a special sense " existential," and that such propositions straight.forwardly attribute the act of exi,stence to an individual or to a class of individuals.1 Some texts seem to support such an interpretation. For example, in his commentary on Aristotle's Perihermeneias, Aquinas says: " To clarify this we must note that the verb 'is ' itself is sometimes predicated in an enunciation, as in ' Socrates is.' By this we intend to signify that Socrates really is." 2 This passage seems to treat the predicate " exists " or " is " as unproblematical , as though it had a straightforward meaning needing little clarification, at least in the context of a logical treatise. On the basis of such a text, one may be tempted to infer that for Aquinas " Socrates exists " has the same logical form as " Socrates sits," and that " Men exist " is of the same form as " Men are mortal.'' Peter Geach has shown, however, that Aquinas's doctrine here is not as simple as it may first appear. For Aquin,as some of the propositions which have the grammatical form of x is have 'a different logical form.3 Geach points out that for Aquinas the sentence, "Blindness exists," for example, actual1 E.g., Etienne Gilson, Being and Some Philosophers, 2nd ed. (Toronto: Pontifical Institute of Mediaeval Studies, 1952), 190-215. 2 Super Peri, Bk. II, lect. 2, # 212. Cf. Summa Contra Gentiles, Bk. II, ch. 37 at "FJ11J hoc ..•." a Peter Geach, in P. T. Geach and G. E. M. Anscombe, Three Philosophers (New York: Cornell University, 1961), 88 ff; Peter Geach, "Form and Existence," in Aquinas: A Collection of Critical Essays, ed. A. Kenny (New York: Notre Dame U., 1969), pp. 41-47. 605 606 PATRICK LEE ly means, Something or other is blind. That is, blind is the real predicate rather than exists. Mo11eover, Geach argues, the logical peculiarity of this sentence is equally found in any sentence of the form, "an F exists." Such a proposition, " does not ,attribute actuality (existence) to an F, but F-ness to something or other ..." 4 And yet Geach will not apply rthis interpretation to all sentences of the form, " x is." He al'lgues that sentences in which " is " or " exists " is. joined to a logically pl'oper name are in a different category. Unlike in general propositions such as "an F exists," in such singular propositions, those using logically proper names, Geach ,argues, actual existence is attributed to or predicated of an individual. "We have here a sense of 'is ' or 'exists ' that seems to me to be certainly a genuine predicate of individuals: the sense of ' exists ' in which one says that an individual came to exist, still exists, no longer exists, etc...."5 I believe that, while Geach's position is more accurate than the first interpretation, mentioned above, it is nevertheless still inaccurate on certain key points. While it is misleading to say that for Aquinas exists is never a genuine predicate; nevertheless , I will argue that it is his position that exists or existence is not a genuine predicate in any proposition which does not refer back to a previous proposition (or to what is known in or by previous propositional knowledge). Let us crull a proposition which refers to something known in a previous proposition a " second-order p11oposition," and one that does not thus refer a " first-order proposition." Then, I shall argue that for Aquinas exists is not a genuine predicate in any first-order proposition. Moreover, I believe that these points are crucial to understanding Aquinas's position on existence as well as his position on how knowledge is related ,to reality, i.e., his realism. In this article I would like to examine Aquinas's thought on the logic of existential propositions and discuss its significance for epistemology . 4 Geach, " Form and Existence," Zoo. int., p. 45. 5 Ibid., p. 46. EXISTENTIAL PROPOSITIONS IN AQUINAS 607 In sections...