 The concept of mental imagery has played an important role in the philosophy of memory for at least two reasons. First, imagery training improves memory (in fact, findings along these lines sparked the revival of research into mental imagery in the 1960s, see Yates 1966, Luria 1960). Second, and more importantly, a fundamental distinction in the philosophy of memory is drawn between episodic and semantic memory (Tulving 1972). To put it very simply, episodic memory is remembering an experience and semantic memory is remembering a fact. And one way of cashing out this difference is in terms of mental imagery: mental imagery is a necessary feature of episodic memory, but not of semantic memory.