The past must be acted by matter, imagined by mind. Memory is not an emanation of matter; indeed the contrary would be nearer the truth if we mean matter as grasped in concrete perception, which always occupies a certain duration.
 Bertrand Russell, A History of Western Philosophy (1945). copy citation

Context

“Apparent failures of memory, it is argued, are not really failures of the mental part of memory, but of the motor mechanism for bringing memory into action. This view is supported by a discussion of brain physiology and the facts of amnesia, from which it is held to result that true memory is not a function of the brain. The past must be acted by matter, imagined by mind. Memory is not an emanation of matter; indeed the contrary would be nearer the truth if we mean matter as grasped in concrete perception, which always occupies a certain duration. “ Memory must be, in principle, a power absolutely independent of matter. If, then, spirit is a reality, it is here, in the phenomena of memory, that we may come into touch with it experimentally. ” “ In pure perception, ” he says, “ we are actually placed outside ourselves, we touch the reality of the object in an immediate intuition. ”” source