 As noted above, the kind of memory on which most recent work has focussed is episodic memory. Episodic memory is, roughly, memory for the events of the personal past, but not just any way of thinking about an event from the personal past amounts to episodically remembering it. On the one hand, it is possible, as noted above, for a subject to remember an event not only episodically but also semantically. Thus one core problem for a theory of episodic remembering is to distinguish between episodic memory and semantic memory, that is, to provide a criterion for the episodicity of episodic memory. The present section discusses attempts to solve this problem, which has received a great deal of attention in recent years. On the other hand, it is possible not only to remember an event but also to imagine it. Thus another core problem for a theory of episodic remembering is to distinguish between episodic memory and episodic imagination, that is, to provide a criterion for the mnemicity of episodic memory. Section 4 discusses attempts to solve this problem, which has historically received more attention.