Bishop Butler's strictures on the topic are known to most students: but, as Sir William Hamilton observes (Foot-note on Reid, pp. 350, 351), "Long before Butler, to whom the merit is usually ascribed, Locke's doctrine of Personal Identity had been attacked and refuted. This was done even by his earliest critic, John Sergeant, whose words, as he is an author wholly unknown to all historians of philosophy, and his works of the rarest, I shall quote. He thus argues:--'The former distinction forelaid, he (Locke) proceeds to make _personal identity in man to consist in the consciousness that we are the same thinking thing in different times and places_. He proves it, because consciousness is inseparable from thinking, and, as it seems to him, _essential_ to it.... But, to speak to the point: Consciousness of any action or other accident we have now, or have had, is nothing but our knowledge that it belonged to us; and, since we both agree that we have no innate knowledges, it follows, that all, both actual and habitual knowledges, which we have, are acquired or accidental to the subject or knower. _Wherefore, the man, or that thing which is to be the knower, must have had individuality or personality, from other principles, antecedently to this knowledge, called consciousness: and, consequently, he will retain his identity, or continue the same man, or (which is equivalent) the same person, as long as he has those individuating principles...._ It being then most evident, _that a man must be the same, ere he can know or be conscious that he is the same_, all his laborious descants and extravagant consequences which are built upon this supposition, that consciousness individuates the person, can need no farther refutation.' "The same objection was also made by Leibnitz in his strictures on Locke's Essay.... "For the best criticism of Locke's doctrine of Personal Identity, I may, however, refer the reader to M. Cousin's '_Cours de Philosophie_.'" One of Locke's arguments is worthy of attention from its oddity. He says (chap. xxvii. 20), "But if it be possible for the same Man to have distinct incommunicable Consciousnesses at different Times, it is past doubt the same Man would at different Times make different Persons; which, we see, is the Sense of Mankind in the solemnest Declaration of their Opinions, Human Laws not punishing the _Mad Man_ for the _Sober Man's_ Actions, nor the _Sober Man_ for what the _Mad Man_ did, thereby making them two Persons; which is somewhat explained by our Way of speaking in _English_, when we say, such a one _is not himself_, or is _besides himself_; in which Phrases it is insinuated, as if those who now, or at least, first used them, thought that _Self_ was changed, the _self_ same Person was no longer in that Man."