Book 7
5
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.The statement that to be a white surface is the same as to be a smooth surface tells us nothing fresh about surface; it simply identifies white with smooth. Aristotle has in mind Democritus’s theory of color (that it is an impression conveyed to our eyes from the superficial texture of the object; Theophrastus, De Sensu 73-75); cf.Aristot. De Sensu 442b 11, Aristot. De Gen. et Corr. 316a 1.
6
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.
7
Let the compound be denoted by X.Literally cloak, but the word is chosen quite arbitrarily. Cf. Aristot. Met. 8.6.4. What is the essence of X?
7
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.
8
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?
