The Substantial Unity of Material Substances according to John Poinsot

THE SUBSTANTIAL UNITY OF MATERIAL SUBSTANCES ACCORDING TO JOHN POINSOT JOHN D. KRONEN The University of St. Thomas St. Paul, Minnesota EVERY SUBSTANCE metaphysician must answer several difficult questions peculiar to his or her ontology. In this paper I will examine John Poinsot's answer to two of these questions, one concerning the nature of the form of substantial composites, and one concerning which material objects are substantial composites. I shall argue that Poinsot's answers to these questions show the untenability of a structuralist view of substantial form and of a reductive materialist view of living beings. But before considering these questions I must briefly outline Poinsot's view of what the general nature of substance is, as explained in his treatise on material logic.1 Poinsot's Account of Substance in General In the section of his Material Logic concerned with the categories Poinsot gives a succinct account of the nature of substance 1 Cursus Philosophicus thomisticus; vol. I, Ars logicae prima et secunda pars, ed. P. Beato Reiser (Turin, Italy: Marietti, 1820), Q. XV, pp. 523-527. It should be noted that I am not concerned in this paper with describing either the psychological origin of the notion of substance, or of justifying it against phenomenalism. My only aim is to show how such a view of substance leads to a certain notion of form when it is applied, so to speak, to material objects. For an interesting account of the origin of the concept of substance in Poinsot see John Deely, Tractatus De Signis: The Semiotic of John Poinsot (Los Angeles, Berkeley, and London: The University of California Press, 1985), p. 86, n. 16. Deely takes it that Poinsot has a deeper categorial scheme than that of Aristotle from which the latter's scheme "emerges," as it were. In this article, then, I am not concerned with that deeper scheme which Deely refers to in this interesting note. 599 600 JOHN D. KRONEN in general and of its relation to the supposit and to the act of existing. He notes that by " substance " narrowly considered is meant that kind of essence to "which it is due to exist in itself as opposed to that kind to which it is due to exist in another" (i.e., an accident).2 He defends this as the primary " definition " 3 of substance against the other definition of it which is " that which stands under accidents," on the grounds that a thing must exist in itself, at least ontologically speaking, before it can support accidents 4 and that to define substance as that which supports accidents is to define it in relation to other things, not itself. This point is important because many modern and contemporary philosophers who have attacked the notion of substance have done so by arguing that there are no beings which stand under accidents . For Poinsot this attack, even if successful, would show that there are no accidents, not that there are no substances. Poinsot insists that " substance " connotes a quiddity to which to exist in itself is due since actual existence does not belong to the essence of any created thing.5 Further, Poinsot insists that to exist in itself " connotes more than a mere negation of existing in another; rather it connotes a positive perfection." This is because to exist in a dependent way is to exist in an imperfect way, so to exist independently must be to exist in a more perfect way.6 Finally, Poinsot distinguishes between the substance and the supposit. The substance is the complete nature of the thing, while 2 Ibid., p. 523. a " Substance " as a supreme genus cannot strictly be defined since it cannot be differentiated from any higher genus. 4 Haec autem proprietas existendi per se intelligitur vel secundum considerationem absolutam et in ordine ad se, et sic dicitur subsistens, quasi non indignes alio ut sustentetur, sed in se sistens; vel dicitur secundum habitudinem ad alia, quatenus ilia sustentat in esse, et sic dicitur non solum subsistens, sed etiam substans. Ibid., p. 523. 5 ••• esse actu per se vel in alio non est ipsa quidditas substantiae vel accidentis , quia esse seu existere in nulla quidditate creata...