Very different would be the logical position of a theory which should assume the existence of an "Unseen World" entirely spiritual in constitution, and in which material conditions like those of the visible world should have neither place nor meaning. Such a world would not consist of ethers or gases or ghosts, but of purely psychical relations akin to such as constitute thoughts and feelings when our minds are least solicited by sense-perceptions. In thus marking off the "Unseen World" from the objective universe of which we have knowledge, our line of demarcation would at least be drawn in the right place. The distinction between psychical and material phenomena is a distinction of a different order from all other distinctions known to philosophy, and it immeasurably transcends all others. The progress of modern discovery has in no respect weakened the force of Descartes's remark, that between that of which the differential attribute is Thought and that of which the differential attribute is Extension, there can be no similarity, no community of nature whatever. By no scientific cunning of experiment or deduction can Thought be weighed or measured or in any way assimilated to such things as may be made the actual or possible objects of sense-perception. Modern discovery, so far from bridging over the chasm between Mind and Matter, tends rather to exhibit the distinction between them as absolute. It has, indeed, been rendered highly probable that every act of consciousness is accompanied by a molecular motion in the cells and fibres of the brain; and materialists have found great comfort in this fact, while theologians and persons of little faith have been very much frightened by it. But since no one ever pretended that thought can go on, under the conditions of the present life, without a brain, one finds it rather hard to sympathize either with the self-congratulations of Dr. Buchner's disciples [8] or with the terrors of their opponents. But what has been less commonly remarked is the fact that when the thought and the molecular movement thus occur simultaneously, in no scientific sense is the thought the product of the molecular movement. The sun-derived energy of motion latent in the food we eat is variously transformed within the organism, until some of it appears as the motion of the molecules of a little globule of nerve-matter in the brain. In a rough way we might thus say that the chemical energy of the food indirectly produces the motion of these little nerve-molecules. But does this motion of nerve-molecules now produce a thought or state of consciousness? By no means. It simply produces some other motion of nerve-molecules, and this in turn produces motion of contraction or expansion in some muscle, or becomes transformed into the chemical energy of some secreting gland. At no point in the whole circuit does a unit of motion disappear as motion to reappear as a unit of consciousness. The physical process is complete in