Psychology may be defined provisionally as science of consciousness - of perception, memory, emotion, and the like. Many psychologists find this definition sufficient as it stands, but, in the view of the writer of this book, does not go far enough. For consciousness does not occur impersonally. Consciousness, on the contrary, always is a somebody-being-conscious. There is never perception without a somebody who perceives, and there never is thinking unless some one thinks. Bearing this fact in mind, we may define psychology more exactly by naming it science of the self as conscious.
Either definition leads at once to a consideration of the meaning of the word 'science.' The scientist is distinguished from the ordinary observer in that he describes exactly and, if possible, explains the objects which both observe. Exact description includes, first, analysis and, second, classification through observed likenesses and differences; explanation consists in linking one fact to allied facts of its own or of another order.