Nature of the imagination.
The imagination is, as it were, a storehouse of forms received through the senses. (ST I, 78, 4.) The existence of this power is obvious through introspection. The imagination is really distinct from the external senses, because an external sense cannot retain the impression of the sense object when this object is no longer acting upon the organ. And it is also distinct from the common sense because the common sense operates only when the external senses are sensing an object. The imagination, on the other hand, produces images of objects even when these objects are absent.
The imagination receives the impressed species from the common sense. It retains these species when actuated by them. The imagination produces as the term of its action an expressed species, called a phantasm. When we use our imagination, we always have an image of the object in which we know the real object.
Functions of the imagination.
The imagination has the following functions:
- To preserve the impressed species that it receives from the common sense–not only the impressed species related to sight, but any impressed species (e.g., that of a melody).
- To combine images or phantasms to form unreal images (artistic ability).
- To know quantity. (Thus the imagination plays an important role in mathematics.)