We submit that psychology _is_ a science, that our sensations, emotions, ideas, etc., can be observed, and can be described scientifically, that is to say, that their uniform sequences and co-existences can be stated with accuracy and formulated as laws. We submit further that our definition of science should be based on facts, and not framed to suit a metaphysical theory. A satisfactory definition of science must include all the sciences. The definition put forward in the interests of the mechanical theory excludes arbitrarily the mental and moral sciences, and implies that their subject-matter is beyond the power of science to deal with. The exclusion and the implication are consequent upon the suggested limitation of science to things moving in space, and are of the essence of the mechanical theory. Both the exclusion and the implication are unnecessary if we adhere to the older conception of science, as it occurs in Mill, which claims for science all phenomena of which the sequences and co-existences can be observed, described, and formulated as laws. What we have said with regard to science applies also of necessity to Evolution. If Evolution is simply the continual redistribution of matter and motion, if matter and motion are the only things subject to evolution, then consciousness and conscience are not subject to evolution. On the other hand, if they too have had and are having their evolution, then the redistribution of matter and motion does not sum up the process of evolution, and is not a correct statement of the process. If it were an induction drawn from a consideration of all the facts of evolution, it would cover them all. But it does not: it excludes a large class of important facts, because their exclusion is demanded in the interests of a particular metaphysical theory--the mechanical theory. It implies that the operation of evolution is confined to a limited set of facts. If the implication is false, then evolution is a bigger thing than the mere redistribution of matter and motion.