Section 4 · Metaphysics

It is convenient to advance to the more intelligible ; for learning is always acquired in this way, by advancing through what is less intelligible by nature to what is more so. And just as in actions it is our task to start from the good of the individual and make absolute good good for the individual, so it is our task to start from what is more intelligible to oneself and make what is by nature intelligible intelligible to oneself.

Now that which is intelligible and primary to individuals is often but slightly intelligible, and contains but little reality; but nevertheless, starting from that which is imperfectly intelligible but intelligible to oneself, we must try to understand the absolutely intelligible; advancing, as we have said, by means of these very things which are intelligible to us.

Since we distinguished at the beginning the number of ways in which substance is defined, and since one of these appeared to be essence, we must investigate this.

First, let us make certain linguistic statements about it.

The essence of each thing is that which it is said to be per se. To be you is not to be cultured, because you are not of your own nature cultured. Your essence, then, is that which you are said to be

of your own nature. But not even all of this is the essence; for the essence is not that which is said to be per se in the sense that whiteness is said to belong to a surface, because being a surface is not being white.

Nor is the essence the combination of both, being a white surface. Why? Because the word itself is repeated. Hence the formula of the essence of each thing is that which defines the term but does not contain it. Thus if being a white surface is the same as being a smooth surface, white and smooth are one and the same.

But since in the other categories too there are compounds with substance (because there is a substrate for each category, e.g. quality, quantity, time, place and motion), we must inquire whether there is a formula of the essence of each one of them; whether these compounds, e.g. white man, also have an essence.

Let the compound be denoted by X. What is the essence of X?

But this is not even a per se expression. We reply that there are two ways in which a definition can be not per se true of its subject: (a) by an addition, and (b) by an omission.

In one case the definition is not per se true because the term which is being defined is combined with something else; as if, e.g., in defining whiteness one were to state the definition of a white man. In the other, because something else (which is not in the definition) is combined with the subject; as if, e.g., X were to denote white man, and X were defined as white. White man is white, but its essence is not to be white. But is to be X an essence at all?

Surely not. The essence is an individual type; but when a subject has something distinct from it predicated of it, it is not an individual type. E.g., white man is not an individual type; that is, assuming that individuality belongs only to substances. Hence essence belongs to all things the account of which is a definition.

We have a definition, not if the name and the account signify the same (for then all accounts would be definitions; because any account can have a name, so that even the Iliad will be a definition), but if the account is of something primary. Such are all statements which do not involve the predication of one thing of another.

Hence essence will belong to nothing except species of a genus, but to these only; for in these the predicate is not considered to be related to the subject by participation or affection, nor as an accident. But of everything else as well, if it has a name, there will be a formula of what it means—that X belongs to Y; or instead of a simple formula one more exact—but no definition, nor essence.

Or perhaps definition, like the what, has more than one sense. For the what in one sense means the substance and the individual, and in another each one of the categories: quantity, quality, etc.

Just as is applies to everything, although not in the same way, but primarily to one thing and secondarily to others; so what it is applies in an unqualified sense to substance, and to other things in a qualified sense. For we might ask also what quality is, so that quality also is a what it is; not however without qualification, but just as in the case of not-being some say by a verbal quibble that not-being is—not in an unqualified sense, but is not-being—so too with quality.

Now although we must also consider how we should express ourselves in each particular case, it is still more important to consider what the facts are. Hence now, since the language which we are using is clear, similarly essence also will belong primarily and simply to substance, and secondarily to other things as well; just as the what it is is not essence simply, but the essence of a quality or quantity.

For it must be either by equivocation that we say that these things are , or by adding and subtracting qualifications, as we say that the unknowable is known ; since the truth is that we use the terms neither equivocally nor in the same sense, but just as we use the term medical in relation to one and the same thing; but not of one and the same thing, nor yet equivocally. The term medical is applied to a body and a function and an instrument, neither equivocally nor in one sense, but in relation to one thing.

However, in whichever way one chooses to speak of these things, it matters nothing; but this point is clear: that the primary and unqualified definition, and the essence, belong to substances. It is true that they belong equally to other things too, but not primarily . For if we assume this, it does not necessarily follow that there is a definition of anything which means the same as any formula; it must mean the same as a particular kind of formula, i.e. the formula of one thing—

one not by continuity like the Iliad, or things which are arbitrarily combined, but in one of the proper senses of one. And one has the same variety of senses as being. Being means sometimes the individual thing, sometimes the quantity, sometimes the quality. Hence even white man will have a formula and definition; but in a different sense from the definition of whiteness and substance.