These various native proclivities that are so classed together as “instincts” have the characteristic in common that they all and several, more or less imperatively, propose an objective end of endeavour. On the other hand what distinguishes one instinct from another is that each sets up a characteristic purpose, aim, or object to be attained, different from the objective end of any other instinct. Instinctive action is teleological, consciously so, and the teleological scope and aim of each instinctive propensity differs characteristically from all the rest. The several instincts are teleological categories, and are, in colloquial usage, distinguished and classed on the ground of their teleological content. As the term is here used, therefore, and indeed as it is currently understood, the instincts are to be defined or described neither in mechanical terms of those anatomical or physiological aptitudes that causally underlie them or that come into action in the functioning of any given instinct, nor in terms of the movements of orientation or taxis involved in the functioning of each. The distinctive feature by the mark of which any given instinct is identified is to be found in the particular character of the purpose to which it drives.[2] “Instinct,” as contra-distinguished from tropismatic action, involves consciousness and adaptation to an end aimed at. It is, of course, not hereby intended to set up or to prescribe a definition of “instinct” at large, but only to indicate as closely as may be what sense is attached to the term as here used. At the same time it is believed that this definition of the concept does violence neither to colloquial usage nor to the usage of such students as have employed the term in scientific discussion, particularly in discussion of the instinctive proclivities of mankind. But it is not to be overlooked that this definition of the term may be found inapplicable, or at least of doubtful service, when applied to those simpler and more immediate impulses that are sometimes by tradition spoken of as “instinctive,” even in human behaviour,--impulses that might with better effect be designated “tropismatic.” In animal behaviour, for instance, as well as in such direct and immediate impulsive human action as is fairly to be classed with animal behaviour, it is often a matter of some perplexity to draw a line between tropismatic activity and instinct. Notoriously, the activities commonly recognised as instinctive differ widely among themselves in respect of the degree of directness or immediacy with which the given response to stimulus takes place. They range in this respect all the way from such reactions as are doubtfully to be distinguished from simple reflex action on the one hand, to such as are doubtfully recognised as instinctive because of the extent to which reflection and deliberation enter into their execution on the other hand. By insensible gradation the lower (less