200 PSYCHOLOGY. fered a breacli. The two ends join each other smoothly- over the gap ; and only the sight of our wound assures us that we must have been living through a time which for our immediate consciousness was non-existent. Even in sleep^this sometimes happens : We think we have had no nap, and it takes the clock to assure us that we are wrong.* We thus may live through a real outward time, a time known by the psychologist who studies us, and yet not feel the time, or infer it from any inward sign. The ques- tion is, how often does this happen ? Is consciousness really discontinuous, incessantly interrupted and recom- mencing (from the psychologist's point of view) ? and does it only seem continuous to itself by an illusion analogous to that of the zoetrope ? Or is it at most times as continu- ous outwardly as it inwardly seems ? It must be confessed that we can give no rigorous answer to this question. Cartesians, who hold that the essence of the soul is to think, can of course solve it a priori, and explain the appearance of thoughtless inter- vals either by lapses in our ordinary memory, or by the sinking of consciousness to a minimal state, in which per- haps all that it feels is a bare existence which leaves no particulars behind to be recalled. If, however, one have no doctrine about the soul or its essence, one is free to take the appearances for what they seem to be, and to admit that the mind, as well as the body, may go to sleep. Locke was the first prominent champion of this latter view, and the pages in which he attacks the Cartesian belief are as spirited as any in his Essay. " Every drowsy nod shakes their doctrine who teach that their soul is always thinking." He will not believe that men so easily forget. M. Jouffroy and Sir W. Hamilton, attacking the question in the same empirical way, are led to an opposite conclusion. Their reasons, briefly stated, are these :
- Messrs. Pay ton Spence (Journal of Spec. Phil, x. 338, xiv. 286)
and M. M. Garver (Amer. Jour, of Science, 3d series, xx. 189) argue, the one from speculative, the other from experimental grounds, that, the physi- cal condition of consciousness being neural vibration, the consciousness must itself be incessantly interrupted by unconsciousness— about fifty times a second, according to Garver.
