On Predicate
in this way the term 'subject' has two senses. In the strict sense we call something a subject with respect to the accidents which really inhere in it and without which it can continue to exist. In the broad sense something is a subject simply because it underlies something else. Here, the object which a subject underlies need not be an accident; it can be the substantial form which informs the subject in question. In the broad sense even matter is said to be a subject with respect to substantial forms.
In another sense a subject is that part of a proposition which precedes the copula and of which something else is predicated. In the proposition 'Man is an animal', 'man' is the subject because 'animal' is predicated of 'man'.
But even here we must distinguish, for in one sense a subject is that which can be the subject in any proposition, true or false. In this sense any universal can be a subject with respect to any other. This comes out in propositions like
'Every animal is a donkey' and 'Every whiteness is a crow'. In another sense a subject is anything that is the subject of a true proposition where there is direct predication. In this sense, 'man' is subject with respect to 'animal', but not vice versa. In a third sense we use the term 'subject' more strictly for that which is the subject of the conclusion ofademonstration, which is or can be known by what, in the strict sense, is called science. Using 'subject' in this sense there are as many subjects in the totality of the sciences as there are conclusions having distinct subjects. Thus there are many subjects in logic as well as in metaphysics and natural philosophy. But in the strictest sense a subject is that which is first in some order ofpriority among those things that are called subjects in the sense just ellucidated. And sometimes the most general among such subjects is called the subject, sometimes the most perfect, and so on with respect to the various orders of priority.
The common trait exhibited by the things we call subject in these different senses is that each is a subject as regards predication.
31: On Predicate A subject we have said is that part of a propositon preceding the copula. In similar fashion we can say that the predicate is that part of a proposition which follows the copula. Nevertheless, some want to say that the predicate is the copula together with what follows it; but since that controversy depends on features peculiar to conventional expressions,
I shall ignore it for the present.