24 THE WORLD AS IDEA.
object; that is to say, that idea which forms the starting-point of the subject's knowledge; because the body, with its immediately known changes, precedes the application of the law of causality, and thus supplies it with its lint data. The whole nature of matter consists as we have seen, in its causal action. But cause and effect exist only for the understanding, which is nothing but their subjective correlative. The understanding, however could never come into operation if there were not something else from which it starts. This is simple sensation — the immediate consciousness of the changes of the body, by virtue of which it is immediate object. Thus the possibility of knowing the world of perception depends upon two conditions; the first, objectively expressed, is the power of material things to act upon each other to produce changes in each other, without which common quality of all bodies no perception would be possible even by means of the sensibility of the animal body And if we wish to express this condition subjectively we say: The understanding first makes perception possible; for the law of causality, the possibility of effect and cause, springs only from the understanding, and is valid only for it, and therefore the world of perception exists only through and for it. The second condition is the sensibility of animal bodies, or the quality of being immediate objects of the subject which certain bodies" possess. The mere modification which the organs of sense sustain from without through their specific affections may here be called ideas, so far as these affections produce neither pain nor pleasure, that is, have no immediate significance for the will, and are yet perceived, exist therefore only for knowledge. Thus far, then, I say that the body is immediately known, is immediate object. But the conception of object is not to be taken here in its fullest sense, for through this immediate knowledge of the body, which precedes the operation of the understanding, and is mere sensation, our own body does not exist
