I. W o r d s like thought and intelligence are commonly applied to complex phases of life which have been gradu­ ally marked off and vaguely apprehended in the course of human culture. More careful study reveals component processes which are variously combined in the complex and shifting phenomena to which such traditional terms are applied. In particular, the distinction between organic intelligence and symbolic processes is of supreme import­ ance in understanding human intellectual activity. There are a group of processes, relatively independent in their structure of any social factors, in which the control of life is centred in all dumb animals; they may be called the processes of organic correlation, or organic intelligence. These processes also underlie human rational intelligence. On the other hand, the structure of human reason is formed, for the most part, of symbolic processes1 (verbal, gestural, etc.) and types of conceptual activity which are dependent in their essential organization upon symbolic processes. And, in turn, these symbolic processes are in large part dependent upon and determined by social processes and organization. The following chapters will deal with the origin of symbolic processes, the causal factors which determine their growth, and the effects of their operation in the reorganization of organic intelligence and in building up the structure of human minds.