However, the situation is not nearly so bad as it at first appears. It is a common experience in all science, when there are two factors, one of which is unknown and uncontrollable, to more or less successfully control the situation by manipulating the other factor. A chemist has a solution and finds by simple tests that it contains an acid. He does not know what acid or how much of it is present. He can neither filter it out nor allow for it, but he can neutralize it and render it harmless by adding an alkali. I t is one of the fundamental facts of psy­ chology that there are two phases of mind, the intellectual and the emotional, each so important and so strong that we commonly speak of an emotional life and an intel­ lectual life.