received; they symbolize the indetermination of the will; on their soundness this indetermination depends; and consequently any injury to these elements, by diminishing our possible action, diminishes perception in the same degree. In other words, if there exist in the material world places where the vibrations received are not mechanically transmitted, if there are, as we said, zones of indetermination, these zones must occur along the path of what is termed the sensori-motor process; and hence all must happen as though the rays Pa, Pb, Pc were perceived along this path and afterwards projected into P. Further, while the indetermination is something which escapes experiment and calculation, this is not the case with the nervous elements by which the impression is received and transmitted. These elements are the special concern of the physiologist and the psychologist; on them all the details of external perception would seem to depend and by them they may be explained. So we may say, if we like, that the disturbance, after having travelled along these nervous elements, after having gained the centre, there changes into a conscious image which is subsequently exteriorized at the point P. But, when we so express ourselves, we merely bow to the exigencies of the scientific method; we in no way describe the real process. There is not, in fact, an unextended image which forms itself in consciousness and then projects itself into P. The truth is that the point P, the rays which it
