to the idea, but from the idea to the perception; and the essential process of recognition is not centripetal, but centrifugal.
Here, indeed, the question arises how stimulation from within can give birth to sensations, either by its action on the cerebral cortex or on other centres. But it is clear enough that we have here only a convenient way of expressing ourselves. Pure memories, as they become actual, tend to bring about, within the body, all the corresponding sensations. But these virtual sensations themselves, in order to become real, must tend to urge the body to action, and to impress upon it those movements and attitudes of which they are the habitual antecedent. The modifications in the centres called sensory, modifications which usually precede movements accomplished or sketched out by the body and of which the normal office is to prepare them while they begin them, are, then, less the real cause of the sensation than the mark of its power and the condition of its efficacy. The progress by which the virtual image realizes itself is nothing else than the series of stages by which this image gradually obtains from the body useful actions or useful attitudes. The stimulation of the so-called sensory centres is the last of these stages: it is the prelude to a motor reaction, the beginning of an action in space. In other words, the virtual image evolves towards the virtual sensation, and the virtual sensation towards real movement: this
