Note 31 — Chapter XXVIII · THEÆTETUS.

The Aristotelian Category of Relation (τὰ πρὸς τί, Categor. p. 6, a. 36) designates one object apprehended and named relatively to some other object — as distinguished from object apprehended and named not thus relatively, which Aristotle considers as per se καθ’ αὑτό (Ethica Nikomach. i. p. 1096, a. 21). Aristotle omits or excludes relativity of the object apprehended to the percipient or concipient subject, which is the sort of relativity directly noted by the Protagorean doctrine.

Occasionally Aristotle passes from relativity in the former sense to relativity in the latter; as when he discusses ἐπιστητὸν and ἐπιστήμη, alluded to in one of my former notes on this dialogue. But he seems unconscious of any transition. In the Categories, Object, as implicated with Subject does not seem to have been distinctly present to his reflection. In the third book of the Metaphysica, indeed, he discusses professedly the opinion of Protagoras; and among his objections against it, one is, that it makes everything relative or πρὸς τί (Metaph. Γ. p. 1011, a. 20, b. 5). This is hardly true in the sense which πρὸς τί bears as one of his Categories: but it is true in the other sense to which I have adverted.

A clear and full exposition of what is meant by the Relativity of Human Knowledge, will be found in Mr. John Stuart Mill’s most recent work, ‘Examination of Sir William Hamilton’s Philosophy,’ ch. ii. pp. 6-15.