predicate is then said to fall under the category of Substance; (2) what _x_ is like, as when I say "_x_ is white, or _x_ is wise,"--the category of Quality; (3) how much or how many _x_ is, as when I say "_x_ is tall" or "_x_ is five feet long,"--the category of Quantity; (4) how _x_ is related to something else, as when I say "_x_ is to the right of _y_," "_x_ is the father of _y_,"--the category of Relation. These are the four chief "categories" discussed by Aristotle. The remainder are (5) Place, (6) Time, (7) and (8) Condition or State, as when I say "_x_ is sitting down" or "_x_ has his armour on,"--(the only distinction between the two cases seems to be that (7) denotes a more permanent state of _x_ than (8)); (9) Action or Activity, as when I say "_x_ is cutting," or generally "_x_ is doing something to _y_"; (10) Passivity, as when I say "_x_ is being cut," or more generally, "so-and-so is being done to _x_." No attempt is made to show that this list of "figures of predication" is complete, or to point out any principle which has been followed in its construction. It also happens that much the same enumeration is incidentally made in one or two passages of Plato. Hence it is not unlikely that the list was taken over by Aristotle as one which would be familiar to pupils who had read their Plato, and therefore convenient for practical purposes. The fivefold classification does depend on a principle pointed out by Aristotle which guarantees its completeness, and is therefore likely to have been thought out by him for himself, and to be the genuine Aristotelian scheme. Consider an ordinary universal affirmative proposition of the form "all _x_s are _y_s." Now if this statement is true it may also be true that "all _y_s are _x_s," or it may not. On the first supposition we have two possible cases, (1) the predicate may state precisely what the subject defined _is_; then _y_ is the Definition of _x_, as when I say that "men are mortal animals, capable of discourse." Here it is also true to say that "mortal animals capable of discourse are men," and Aristotle regards the predicate "mortal animal capable of discourse" as expressing the inmost nature of man. (2) The predicate may not express the inmost nature of the subject, and yet may belong only to the class denoted by the subject and to every member of that class. The predicate is then called a Proprium or property, an exclusive attribute of the class in question. Thus it was held that "all men are capable of laughter" and "all beings capable of laughter are men," but that the capacity for laughter is no part of the inmost nature or "real essence" of humanity. It is therefore reckoned as a Proprium.