DIFFERENCE IN EFFECTS IS LIMITED TO THE INTELLIGIBLES.
A further possibility is that these things should be classified according to their effects, and that it is reasonable to do so with invisible entities, such as sciences; but this would not be applicable to sense-objects. When indeed we divide sciences by their effects, and when, in general, we classify them according to the powers of the soul, by concluding from the diversity of their effects that they differ, our mind grasps the difference of these powers, and it determines not only with what objects they deal, but it also defines their reason (or, essence). Let us admit that it is easy to distinguish arts according to their reasons, and according to the notions they include; but is it possible to divide corporeal qualities in that manner? Even when one studies the intelligible world, there is room for doubt as to how the different reasons distinguish themselves from each other; it is easy enough to see that white differs from black; but in what does it do so?