 These results show that episodic memory involves the exercise of mental imagery, but it is an open debate whether there is more to episodic memory than mental imagery. Some have argued that episodic memory has some extra ingredients besides mental imagery, for example, some sort of causal chain to the past observed event (e.g., Bernecker 2010). In contrast, some other philosophers of memory claim that episodic memory is really nothing but mental imagery (Michaelian 2016, De Brigard 2014, Hopkins 2018). The claim is that there is no real difference between future-directed mental time travel (that is, imagining the future) and past-directed mental time travel (episodic memory). Whether we go with the stronger or the weaker claim about the importance of mental imagery in memory, understanding memory seems to presuppose understanding mental imagery.