  Reid traces the target of his criticisms back to the Ancients, whom he depicts as holding that the mind is a sensorium—a repository of past ideas and impressions (Essays,  280).[1]   On this theory, perception, memory and imagination are causal processes beginning with purely physiological events: impressions on the brain. These physiological states are taken to have mental correlates—sensations or ideas of sense or sense impressions—which are the objects of perception, memory and imagination. These ideas or impressions are representations in the sense that they preserve, or re-present information from their physiological correlates.  According to Reid, this view recognizes no distinction between imagination and memory. Each consists in having a picture-like impression that remains after the object that impressed upon the senses is gone. The only difference between the two is in the fidelity of the imagistic impression to its cause. Memory consists in the preservation of images imprinted in the mind from previous experiences, while imagination consists in constructing images that lack a duplicate in experience.