See the Inquiry concerning Virtue or Merit, pt. iii, § 2; and the Letters to a Student, under date June 3, 1709 (p. 403 in Rand's Life, Letters, etc., of Shaftesbury, 1900). The extraordinary letter of Newton to Locke, written just after or during a spell of insanity, first apologizes for having believed that Locke "endeavoured to embroil me with women and by other means," and goes on to beg pardon "for representing that you struck at the root of morality, in a principle you laid down in your book of ideas." In his subsequent letter, replying to that of Locke granting forgiveness and gently asking for details, he writes: "What I said of your book I remember not." (Letters of September 16 and October 5, 1693, given in Fox Bourne's Life of Locke, ii, 226-27, and Sir D. Brewster's Memoirs of Sir Isaac Newton, 1855, ii, 148-51.) Newton, who had been on very friendly terms with Locke, must have been repeating, when his mind was disordered, criticisms otherwise current. After printing in full the letters above cited, Brewster insists, on his principle of sacrificing all other considerations to Newton's glory (cp. De Morgan, Newton: his Friend: and his Niece, 1885, pp. 99-111), that all the while Newton was "in the full possession of his mental powers." The whole diction of the first letter tells the contrary. If we are not to suppose that Newton had been temporarily insane, we must think of his judgment as even less rational, apart from physics, than it is seen to be in his dissertations on prophecy. Certainly Newton was at all times apt to be suspicious of his friends to the point of moral disease (see his attack on Montague, in his letter to Locke of January 26, 1691-1692; in Fox Bourne, ii, 218; and cp. De Morgan, as cited, p. 146); but the letter to Locke indicates a point at which the normal malady had upset the mental balance. It remains, nevertheless, part of the evidence as to bitter orthodox criticism of Locke.