attainment of this end-identity; by substituting one idea for the other they deviate from the path which otherwise would have been continued from the original idea.

Such processes are therefore carefully avoided in the secondary thinking. Nor is it difficult to understand that the principle of pain also impedes the progress of the mental stream in its pursuit of the thought identity, though, indeed, it offers to the mental stream the most important points of departure. Hence the tendency of the thinking process must be to free itself more and more from exclusive adjustment by the principle of pain, and through the working of the mind to restrict the affective development to that minimum which is necessary as a signal. This refinement of the activity must have been attained through a recent over-occupation of energy