The general opinion of mankind has usually considered thought-processes to be of a very mysterious nature. Thought-processes, just as sensory or emotional processes, are part-reactions within a given unit response. The incoming impulses from the sensory centres, either in sensory groups or as already integrated into percepts in the outlying correlation centres, cannot long avoid meeting and therefore combining with groups of typical correlation impulses already passing in various directions through the correlation centres. Neurologically the human nervous system achieves its utmost refinement and complexity in the correlation system of the cerebrum. The dominant thought-process is, fairly easy to isolate by analysis from the more involved compound intellectual responses in which it occurs. Advertising in peace time and propaganda during war rely upon the submissive intellectual tendency of those addressed.