The result of atomism in any form, dealing with any subject, is that the principle of uniformity is hunted down into the elements of things; it is resolved into the uniformity of these elements or atoms, and of the relations of those which are next to each other. By an element or an atom we do not here mean something absolutely simple or indivisible, for a molecule, a brick, and a nerve-process are all very complex things. We only mean that, for the purpose in hand, the properties of the still more complex thing which is made of them have nothing to do with the complexities or the differences of these elements. The solid made of molecules, the house made of bricks, the nervous system made of sensori-motor processes, are nothing more than collections of these practically uniform elements, having certain relations of nextness, and behavior uniformly depending on that nextness. The inference of phenomena from phenomena, then, is based upon an assumption of uniformity, which in the present stage of science may be called an atomic uniformity. The other mode of inference which belongs to the scientific method is that which is used in what are called the mental and moral sciences; and it enables us to go from phenomena to the facts which underlie phenomena, and which are themselves not phenomena at all. If I pinch your arm, and you draw it away and make a face, I infer that you have felt pain. I infer this by assuming that you have a consciousness similar to my own, and related to your perception of your body as my consciousness is related to my perception of my body. Now is this the same assumption as before, a mere assumption of the uniformity of nature? It certainly seems like it at first; but if we think about it we shall find that there is a very profound difference between them. In physical inference I go from phenomena to phenomena; that is, from the knowledge of certain appearances or representations actually present to my mind I infer certain other appearances that might be present to my mind. From the weight of a stone in the morning--that is, from my feeling of its weight, or my perception of the process of weighing it, I infer that the stone will be heavy in the afternoon--that is, I infer the possibility of similar feelings and perceptions in me at another time. The whole process relates to me and my perceptions, to things contained in my mind. But when I infer that you are conscious from what you say or do, I pass from that which is my feeling or perception, which is in my mind and part of me, to that which is not my feeling at all, which is outside me altogether, namely, your feelings and perceptions. Now there is no possible physical inference, no inference of phenomena from phenomena, that will help me over that gulf. I am obliged to admit that this second kind of inference depends upon another assumption, not included in the assumption of the uniformity of phenomena.