[14] Socrates' reference of a discussion to its presuppositions (Xenophon, _Mem._ iv. 6, 13) is not relevant for the history of the terminology of induction. [15] _Theaetetus_, 186c. [16] Timaeus, 37a, b (quoted in H. F. Carlill's translation of the _Theaetetus_, p. 60). [17] _Theaetetus_, 186d. [18] Sophistes, 253d. [19] _Ib. id._; cf. _Theaetetus_, 197d. [20] Aristotle, _de An._ 430b 5, and generally iii. 2, iii. 5. [21] For Plato's Logic, the controversies as to the genuineness of the dialogues may be treated summarily. The _Theaetetus_ labours under no suspicion. The _Sophistes_ is apparently matter for animadversion by Aristotle in the _Metaphysics_ and elsewhere, but derives stronger support from the testimonies to the _Politicus_ which presumes it. The _Politicus_ and _Philebus_ are guaranteed by the use made of them in Aristotle's Ethics. The rejection of the _Parmenides_ would involve the paradox of a nameless contemporary of Plato and Aristotle who was inferior as a metaphysician to neither. No other dialogue adds anything to the _logical_ content of these. Granted their genuineness, the relative dating of three of them is given, viz. _Theaetetus_, _Sophistes_ and _Politicus_ in the order named. The _Philebus_ seems to presuppose _Politicus_, 283-284, but if this be an error, it will affect the logical theory not at all. There remains the _Parmenides_. It can scarcely be later than the _Sophistes_. The antinomies with which it concludes are more naturally taken as a prelude to the discussion of the _Sophistes_ than as an unnecessary retreatment of the doctrine of the one and the many in a more negative form. It may well be earlier than the _Theaetetus_ in its present form. The stylistic argument shows the _Theaetetus_ relatively early. The maturity of its philosophic outlook tends to give it a place relatively advanced in the Platonic canon. To meet the problem here raised, the theory has been devised of an earlier and a later version. The first may have linked on to the series of Plato's dialogues of search, and to put the _Parmenides_ before it is impossible. The second, though it might still have preceded the _Parmenides_ might equally well have followed the negative criticism of that dialogue, as the beginning of reconstruction. For Plato's logic this question only has interest on account of the introduction of an [Greek: Aristotelês] in a non-speaking part in the _Parmenides_. If this be pressed as suggesting that the philosopher Aristotle was already in full activity at the date of writing, it is of importance to know what Platonic dialogues were later than the début of his critical pupil.