According to a current theory, imagination is the faculty that enables us to see objects in their concrete form. While imagining things, therefore, the mind is sometimes led to wonder if it's in the presence of a real object or just a conception. This distinguishes imagination from understanding – the latter generalizes, eliminating all that's particular and unique about an object, where the former leaves its object with its personal characteristics, granting a new life and a new depth to its individuality.

This applies to the three forms of imagination – reproduction, combination, and creation. Let's study each of these three forms in turn, noting their differences.

1. Imaginative Memory. Memory weakens past states of consciousness as it reproduces them because it abstracts, remembering primarily that which is general. For this reason, a man who has memory but lacks imagination will tend to forget everything that's unique about a state of consciousness. Imaginative memory, however, reproduces previously perceived objects under forms as concrete as those provided by perception. The resemblance can be so vivid that the mind may be fooled.

But imaginative memory goes no further than this, reproducing faithfully only what's been previously experienced. It's not passive – no faculty is – but it creates nothing new, merely repeating our past life and primarily reproducing sensations. Now, it's often been asked if imaginative memory reproduces all sensations or only some. Clearly, it's most active when it comes to visual sensations, but it reproduces sensations of sound just as well.