The two remaining categories include everything which may be excluded from the conception of a thing on the ground of being either non-essential or accidental. In as far as such things belong to an object taken by itself alone, they come under the category of variety (πὼς ἔχον); but when they belong to it, because of its relation to something else, they come under the category of variety of relation (πρός τί πως ἔχον). Variety includes all accidental qualities, which can be assigned to any object independently of its relation to any other object. [202] Size, colour, place, time, action, passion, possession, motion, state, in short, all the Aristotelian categories, with the exception of substance, whenever they apply to an object independently of its relation to other objects, belong to the category of variety [203] (πὼς ἔχον). On the other hand, those features and states which are purely relative—such as right and left, sonship and fatherhood, &c.—come under the category of variety of relation (πρός τί πως ἔχον); and from this category the simple notion of relation (πρὸς τὶ) must be distinguished. Simple relation (πρὸς τὶ) is not treated as a distinct category, since it includes not only accidental relations, but also those essential properties (ποιὰ) which presuppose a definite relation to something else—such as knowledge and perception. [204] [(c) Relation of the categories to one another.] The relation of these four categories to one another is such, that each preceding category is included in the one next following, and receives from it a more definite character. [205] Substance never occurs in reality without property, but has always some definite quality to give it a character. On the other hand, property is never met with alone, but always in connection with some subject-matter. [206] Variety presupposes some definite substance, and variety of relation supposes the existence of variety. [207] It will hereafter be seen how closely these deductions, and, indeed, the whole doctrine of the categories, depend on the metaphysical peculiarities of the Stoic system. [(3) Complete utterance.] [(a) Judgment.]