A. About the Nature or Definition of Transubstantiation

14. On the first point I say that this is the common idea of this name ‘transubstantiation’: transubstantiation is the total transition of substance into substance.

15. First I explain the term ‘total’; for a whole, a totality, is in one way said to be something completed from parts; in another way for any part categorematically or syncategorematically.William of Sherwood, Syncategoremata: “A ‘whole’ sometimes states the totality of something according as it is a thing, and it is equivalent to that which is integral or complete, and is a category term [a predicate or subject]. Sometimes it states the totality of something with respect to a predicate and is a syncategorematic term [additional to or modifying predicate or subject], and amounts, as is said, to the same as ‘each part whatever’ and is a sign of universality.” ²⁰

16. Accordingly, there can be a transition of a whole into a whole in two ways:

In one way, when taking ‘whole’ for a whole complete with its parts, according as there succeeds to one whole of parts another whole of parts. And in this way the Philosopher, On Generation 1.2.317a20-22, says that generation is the change of a whole into a whole, because the whole of parts that was truly ‘a per se one whole’ does not remain but another whole succeeds to it - not, however, that each part succeeds, because, in his view, the matter remains common.

17. And, by contrast, there is no transition of whole into whole in the case of alteration (because each whole per se one, which precedes the alteration, remains at the term of the alteration), but one whole passes over only in a certain respect, or per accidens, into another whole per accidens (as hot wood passes into cold wood), neither of which is a whole properly speaking but only a whole per accidens, just as it is one per accidens.Hot wood is a combination of a subject, wood, and a property or accident, hot, and the subject does not change when the wood becomes cold but only the property or accident of heat in the subject. ²¹

18. Now each whole, which, namely, is per se one, and consequently is a whole in the genus of substance, remains the same under each term of this sort of change [sc. alteration, n.17].

19. Hereby is plain that this authority of Aristotle [n.16] does not make anything against the position about the plurality of forms [Ord. III d.2 nn.108-113], because however much the first form is posited as remaining (according to material identity) in the generated and corrupted thing, yet the same whole does not remain (even in this way of speaking of whole), because the whole that simply preceded corruption included the specific ultimate form, and that form does not remain in the term of generation but only a part of it does.

20. Therefore was it well said in the definition of transubstantiation [n.14], by way of distinguishing it from transmutation or alteration, not that transubstantiation is the transition of ‘whole into whole’ (for then there could be equivocation over the term ‘whole’Sc. ‘whole’ could mean ‘whole substance’ (e.g. wood) or ‘whole of substance and accidents’ (e.g. hot wood). ²²), but that it is ‘total’ transition.

21. About the second part added to this idea of the name [n.15], that is, ‘substance into substance’, I say that ‘substance’ there is posited in distinction from ‘accident’ - as is manifest, because transition of accident into accident would be called ‘trans-accidentation’ rather than ‘transubstantiation’. But as to what is said about ‘substance into substance’, it must be understood according to the Philosopher in Physics 1.6.189a34-b16, that in two ways is something said to come to be from something, namely either from a subject that remains or from a term that is corrupted (for fire comes from the matter of fire in one way, and from air or non-fire in another way, according to him ibid.).

22. The partial transition, then, of substance into substance can be either of a subject passing from term to term [sc. fire coming to be from fire] or of a whole term passing into the opposite term [sc. fire coming to be from air].

23. But in the issue at hand [sc. transubstantiation], when ‘total transition’ is spoken of, the first understanding is excluded, for nothing common in this case passes from term to term (for then the transition would not be total but partial); so there is only transition of substance into substance as of a term totally ceasing to be into a term (as into a substance) totally beginning to be.