PSYCHOLOGICAL PKINCIPLES. (ill.) 59

scrutinise the dot on an i and go on thinking. Intoxication, hypnotism or insanity, rest or exhaustion, tells on apper- ception as well as on innervation. The control of thoughts equally with the control of movements requires "effort"; and, as there is a strain peculiar to intently listening or gazing, which is known to have a muscular concomitant, so too there is a strain equally characteristic of recollection and visualisa- tion, which may quite well turn out to be muscular too. "When movements have to be associated the same continuous attention is called for as is found requisite to associate sen- sory impressions : when such associations have become very intimate dissociation is about equally difficult in both cases. The process of control is also, so far as we yet know, much the same : it is a process of direct repression or of alternative intensification, or a combination of both. One real difference there is, no doubt : movements ensue either through the withdrawal of inhibition or through a concentration of atten- tion on the idea of the movement. The like, it need hardly be said, does not hold of sensations ; though in abnormal cases there is an indefinitely close approach to it. "If ifs and ans were pots and pans there'd be no trade for tinkers " nay, more, there'd be no trade for movements of any sort, except so far as these were pleasurable in themselves. It is just this difference in the objects that makes all the differ- ence in our attitude, but it is not a difference in the psychical activity concerned with them. There is further a supposed difference between apper- ception and innervation, or rather between what are assumed to be their physiological concomitants, which has stood in the way of their identification. Appercep- tion is assumed to be related to afferent nerve-currents ; and innervation, on the contrary, to efferent currents. Prof. Bain complains that in the article he criticises no notice is taken of this position. It is true no notice was taken, and for what seemed to be good reasons. In the first place, it is not a matter that concerns psychology proper at all. When psycho- logists as such are sure of their facts and neurologists in like manner sure of theirs, we may expect a great advance of know- ledge from careful endeavours to correlate the two. A hopeful beginning has indeed already been made; but meanwhile the most disastrous confusion has befallen the more difficult inquiry through plausible but hasty interpretations of un- verified physiological hypotheses. Psychologically we know nothing of nerve-currents, whether afferent or efferent. But in the next place, it is, to say the least, extremely question- able whether muscular efforts are the concomitant of what