place of motives, where, through these, the will becomes choice, i.e., becomes more definitely determined by motives. These motives are ideas, which, on the occasion of external stimuli of the organs of sense, arise by means of the functions of the brain, and are also worked up into conceptions, and then into resolves. When it comes to the real act of will these motives, the workshop of which is the cerebrum, act through the medium of the cerebellum upon the spinal cord and the motor nerves which proceed from it, which then act upon the muscles, yet merely as stimuli of their irritability; for galvanic, chemical, and even mechanical stimuli can effect the same contraction which the motor nerve calls forth. Thus what was motive in the brain acts, when it reaches the muscle through the nerves, as mere stimulus. Sensibility in itself is quite unable to contract a muscle. This_can only be done by the muscle itself, and its capacity for doing so is called irritability, i.e., susceptibility to stimuli. It is exclusively a property of the muscle, as sensibility is exclusively a property of the nerve. The latter indeed gives the muscle the occasion for its contraction, but it is by no means it that, in some mechanical way, draws the muscle together; but this happens simply and solely on account of the irritability, which is a power of the muscle itself. Apprehended from without this is a Qualitas occulta, and only self-consciousness reveals it as the will. In the causal chain here briefly set forth, from the effect of the motive lying outside us to the contraction of the muscle, the will does not in some way come in as the last link of the chain; but it is the metaphysical substratum of the irritability of the muscle: thus it plays here precisely the same part which in a physical or chemical chain of causes is played by the mysterious forces of nature which lie at the foundation of the process – forces which as such are not themselves involved as links in the causal chain, but impart to all the links of it the capacity to act, as I have fully shown in § 26 of the first volume. Therefore we would ascribe the contraction of the muscle also to a similar mysterious
