In the perception of a tree we can distinguish the act of experiencing, or perceiving, from the thing experienced, or perceived.

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.

The perceptive act is a reaction of the mind upon the object of which it is the perception.

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.

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

The sensory acts are accordingly distinguished by their objects.

An object is not first imagined or thought about and then expected or willed, but in being actively expected it is imagined as future and in being willed it is thought.