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of knowledge as a means of determining the individual manifestations of this omnipresent will and as a mediator between the outer world and the changes of such a being; finally, in inorganic Nature, it is physical agency in general; and when, as here, observation takes place from a higher to a lower degree, both stimulus and physical agency present themselves as substitutes for knowledge, therefore as mere analogues to it. Plants cannot properly be said to perceive light and the sun; yet we see them sensitive in various ways to the presence or absence of both. We see them incline and turn towards the light; and though this movement no doubt generally coincides with their growth, just as the moon's rotation on its axis coincides with its movement round the earth, it nevertheless exists, as well as that of the moon, and the direction of that growth is determined and systematically modified by light, just as an action is determined by a motive, and as the direction of the growth of creeping and clinging plants is determined by the shape and position of the supports they may chance to find. Thus because plants on the whole still have wants, though not such wants as demand the luxury of a sensorium and an intellect, some thing analogous has to take the place of these, in order to enable the will to lay hold of, if not to seek out, the satisfactions which offer themselves to it. Now, this analogous substitute is susceptibility for stimuli, and I would express the difference between knowledge and this susceptibility as follows: in knowledge, the motive which presents itself as representation and the act of volition which follows from it, remain distinctly separate one from the other, this separation moreover being the more distinct, the greater the perfection of the intellect; whereas, in mere susceptibility for stimuli, the feeling of the stimulus can no longer be distinguished from the volition it occasions, and they coalesce. In inorganic nature finally, even susceptibility
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