volume rests upon the assumption, which has just been criticised, of an objective and a subjective world both in space, and upon the impossibility which arises in connection with this presupposition of a transition from, one to the other, a bridge between the two. Upon this controversy I have still to add the following remarks.
The subjective and the objective do not constitute a continuous whole. That of which we are immediately conscious is bounded by the skin, or rat her by the extreme ends of the nerves which proceed from the cerebral system. Beyond this lies a world of which we have no knowledge except through pictures in our head. Now the question is, whether and how far there is a world independent of us which corresponds to these pictures. The relation between the two could only be brought about by means of the law of causality; for this law alone leads from what is given to something quite different from it. But this law itself has first of all to prove its validity. Now it must either be of objective or of subjective origin; but in either case it lies upon one or the other side, and therefore cannot supply the bridge between them. If, as Locke and Hume assume, it is a posteriori, thus drawn from experience, it is of objective origin, and belongs then itself to the external world which is in question. Therefore it cannot attest the reality of this world, for then, according to Locke s method, causality would be proved from experience, and the reality of experience from causality. If, on the contrary, it is given a priori, as Kant has more correctly taught us, then it is of subjective origin, and in that case it is clear that with it we remain always in the subjective sphere. For all that is actually given empirically in perception is the occurrence of a sensation in the organ of sense; and the assumption that this, even in general, must have a cause rests upon a law which is rooted in the form of our knowledge, i.e., in the functions of our brain. The origin of this law is therefore just as subjective as that of the sensation itself. The cause of the
