had applied his method to the theoretical side of philosophy led him on to extend it to the practical. Here also he endeavoured to separate pure a priori from empirical a posteriori knowledge. For this purpose he assumed that just as we know a priori the laws of Space, of Time, and of Causality, so in like manner, or at any rate analogously, we have the moral plumb-line for our conduct given us prior to all experience, and revealed in a Categorical Imperative, an absolute “Ought.” But how wide is the difference between this alleged moral law a priori, and our theoretical knowledge a priori of Space, Time, and Causality!

The latter are nothing but the expression of the forms, i.e., the functions of our intellect, whereby alone we are capable of grasping an objective world, and wherein alone it can be mirrored;