Although we know that reason is attached to perceptible matter, to physical objects, so that science can never be anything else but the science of the physical, still we may, according to the prevailing ideas and usage of language, separate physics from logic and ethics, and thus distinguish them as different forms of science. The problem is then to demonstrate that in physics as well as in logic, as also in ethics, the general or intellectual perceptions can be practically obtained only on the basis of concrete perceptible facts. This practice of reason, to generate thought from matter, to arrive at understanding by sense perceptions, to produce the general out of the concrete, has been universally accepted in physical investigation, but only in practice. The inductive method is employed, and one is aware of this fact, but it is not understood that the nature of inductive science is the nature of science in general, of reason. The process of thought is misunderstood. Physical science lacks the theory of understanding and for this reason often falls out of its practical step. The faculty of thought is still an unknown, mysterious, mystical being for natural science. Either it confounds the function with the organ, the mind with the brain, as do the materialists, or it thinks with the idealists that the faculty of thought is an imperceptible object outside of its field. We see modern investigators marching toward their goal with firm and uniform steps, so far as physical matters are concerned. But they aimlessly grope around in the abstract relations of these things. The inductive method has been practically adopted by natural science and its successes have secured a great reputation for it. On the other hand, the speculative method has become discredited by its failures. There is, however, no conscious understanding of these various methods of thought. We see the men of physical research, when they are outside of their special field, offer lawyer-like speculations in lieu of scientific facts. While they arrive at the special truths of their chosen fields by sense perceptions, they still pretend to derive speculative truths out of the depths of their own minds.