Page:Philosophical Review Volume 2.djvu/691

 ENTAL Phenomena and Physical Phenomena.–Experimental psychology, like every empirical science, starts with the facts of our immediate experience. The innumerable phenomena which we experience directly, i. e., of which we are conscious, fall naturally into various classes according to the point of view we happen to take. One of the divisions is that into sights, sounds, tastes, etc., on the one hand, and impulses, emotions, memories, etc., on the other. Just what distinguishing characteristics we find in each class it is impossible to say. Indeed, the division is not at all complete or distinct; many experiences that we on one occasion put into one class, e. g., hallucinations which we believe to be realities, we at another time place in the other, e. g., hallucinations recognized as such; in very many cases we are in doubt as to which class a certain experience belongs. The experiences of the former class we regard as belonging to an objective world, as we call it; those of the latter, and in some degree those of the former, to a subjective world. The objective class consists, by supposition, of phenomena constant in character for constant objective conditions; the actual variations in these phenomena under constant objective conditions we ascribe to mental elements. For example, we consider colors to be phenomena of the objective world (I am speaking from a purely introspective standpoint); under the most careful physical conditions we can maintain the color in a condition which we know by secondary means to be constant within a very small range of variation. Yet the color actually experienced will be subject to considerable variations; these we ascribe to the influence of mental phenomena, e. g., attention, fatigue, etc. Suppose we wish to compare two colors together; we so arrange matters that the two classes of variations, the physical and the psychological, are kept as small