The assumption that it is easier to measure a part, or one aspect, of intelligence than all of it, is fallacious in that the parts are not separate parts and cannot be separated by any refinement of experiment. They are interwoven and intertwined. Each ramifies everywhere and appears in all other functions. The analogy of the stones of the tower does not really apply. Memory, for example, cannot be tested separately from attention, or sense-discrimination separately from the associative processes. After many vain attempts to disentangle the various intellective functions, Binet decided to test their combined functional capacity without any pretense of measuring the exact contribution of each to the total product. It is hardly too much to say that intelligence tests have been successful just to the extent to which they have been guided by this aim. Memory, attention, imagination, etc., are terms of "structural psychology." Binet's psychology is dynamic. He conceives intelligence as the sum total of those thought processes which consist in mental adaptation. This adaptation is not explicable in terms of the old mental "faculties." No one of these can explain a single thought process, for such process always involves the participation of many functions whose separate rôles are impossible to distinguish accurately. Instead of measuring the intensity of various mental states (psycho-physics), it is more enlightening to measure their combined effect on adaptation. Using a biological comparison, Binet says the old "faculties" correspond to the separate tissues of an animal or plant, while his own "scheme of thought" corresponds to the functioning organ itself. For Binet, psychology is the science of behavior. BINET'S CONCEPTION OF GENERAL INTELLIGENCE. In devising tests of intelligence it is, of course, necessary to be guided by some assumption, or assumptions, regarding the nature of intelligence. To adopt any other course is to depend for success upon happy chance.