Psychology is the science of the act of experiencing, and deals with the whole system of such acts as they make up mental life.
What is the meaning of the togetherness of the perceiving mind, in that peculiar modification of perceiving which makes it perceive not a star but a tree, and the tree itself, is a problem for philosophy.
Both expectations and memories are more than mere images founded on previous experience.
We cannot therefore say that mental acts contain a cognitive as well as a conative element.
Thus the same object may supply a practical perception to one person and a speculative one to another, or the same person may perceive it partly practically and partly speculatively.
When we come to images or memories or thoughts, speculation, while always closely related to practice, is more explicit, and it is in fact not immediately obvious that such processes can be described in any sense as practical.
It is more difficult to designate this form of conation on its practical side by a satisfactory name.
For psychological purposes the most important differences in conation are those in virtue of which the object is revealed as sensed or perceived or imaged or remembered or thought.
An expectation is a future object, recognised as belonging to me.
But though cognition is not an element of mental action, nor even in any real sense of the word an aspect of it, the distinction of cognition and conation has if properly defined a definite value.
But unfortunately Locke treated ideas of reflection as if they were another class of objects of contemplation beside ideas of sensation.
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.
Hence, in desiring, the more the enjoyment is delayed, the more fancy begins to weave about the object images of future fruition, and to clothe the desired object with properties calculated to inflame the impulse.
In the perception of a tree we can distinguish the act of experiencing, or perceiving, from the thing experienced, or perceived.
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.
It may be added, to prevent misunderstanding, that when I speak of contemplated objects in this last phrase as objects of contemplation, the act of contemplation itself is of course an enjoyment.