Ockham says that existence as such is particular as opposed to universal. St. Thomas implicitly denies this when he omits “particular” as a transcendental. If “particular” belonged to being or existence as such, it would be convertible with it. St. Thomas also says in his discussion of “person” that “individual” or “particular” is an intentional term- that is, it is proper to logic and not to the science of being as such.
On St. Thomas’s account, Ockham errs by confusing logic and metaphysics. Contraries must be in the same genus, and everyone agrees that “universal” belongs only to the order of logical existence. How is it, then that we can say that existence is particular? In St. Thomas’s account, so long as one is speaking about the particular as opposed to the universal, the existent is neither particular nor universal. However, there is no necessity that one must use the terms “particular” or “individual” only in the logical order- St. Thomas himself uses the term “individual” in the definition of a person, and he could have just as easily used particular. St. Thomas even explains why he had to borrow a term from the logical order to speak about things outside the logical order, and his explanation makes it clear why we would assume that “particular” or individual belong to the existent order. First the objection to give context:
an intentional term must not be included in the definition of a thing. For to define a man as “a species of animal” would not be a correct definition; since man is the name of a thing, and “species” is a name of an intention. Therefore, since person is the name of a thing (for it signifies a substance of a rational nature the word “individual” which is an intentional name comes improperly into the definition.
and his response:
Substantial differences being unknown to us, or at least unnamed by us, it is sometimes necessary to use accidental differences in the place of substantial; as, for example, we may say that fire is a simple, hot, and dry body: for proper accidents are the effects of substantial forms, and make them known. Likewise, terms expressive of intention can be used in defining realities if used to signify things which are unnamed. And so the term “individual” is placed in the definition of person to signify the mode of subsistence which belongs to particular substances
Notice that the reason we need to borrow from the logical order is our failure to know the existent order. Since we can only name as we know, it follows that we must use the word “particular” in the existent order, because we don’t know the very thing we would name particular as existent. We don’t know, as it were, the “true name” of the individual existent, and so we borrow a term that belongs to it properly as known. Such a need to borrow makes it all but inevitable that even very wise men would confuse “particular” as belonging to the logical order, and as belonging to the existent order.
If Ockham’s argument about universals is grounded in saying that what exists is particular as opposed to universal then St. Thomas would say that Ockham is commiting the same error as Plato, but he draws the only other possible conclusion. For St. Thomas, Plato says that logical things existed simply, but he says that the real is the universal as opposed to particular; while Ockham also says that logical things exist simply, but the real is the particular as opposed to the universal. Thomists take the only option left- logical things do not exist simply, and so the real is neither universal nor particular as opposed to universal.