Such being the nature of mental life, the business of psychology is primarily to describe in detail the various forms which attention or conation assumes upon the different levels of that life.

Psychology is the science of the act of experiencing, and deals with the whole system of such acts as they make up mental life.

Curiosity begins as an act of tearing to pieces or analysis.

The sensory acts are accordingly distinguished by their objects.

It is more difficult to designate this form of conation on its practical side by a satisfactory name.

Desire then is the invasion of the whole self by the wish, which, as it invades, sets going more and more of the psychical processes; but at the same time, so long as it remains desire, does not succeed in getting possession of the self.

It is convenient to distinguish the two kinds of experience which have thus been described, the experienc-ing and the experienc-ed, by technical words.