 Philosophers committed to the traditional view of the difference between memory and imagination are likely to object not only to this implication of the simulation theory but also to the idea of mental time travel itself. Research on mental time travel, as we have seen, suggests that there is no qualitative difference between episodic memory and episodic future thought. Adopting Perrin’s (2016) terminology, continuists argue explicitly that any difference between them is merely quantitative, while discontinuists grant that there are quantitative similarities between episodic memory and episodic future thought but maintain that there are a variety of qualitative differences between them. Discontinuism is the traditional view. Debus (2014), for example, has drawn on relationalist accounts of the objects of episodic memory (J. Campbell 2001; Debus 2008; see section 5 below) to argue that, when one remembers a past event, the remembered event itself may, due to one’s previous causal contact with it, constitute part of the content of one’s mental state, whereas, when one imagines a future event, the imagined event cannot constitute part of the content of one’s mental state, because one has had no causal contact with it. Perrin (2016), meanwhile, has argued that, when one imagines a future event, one effectively stipulates the identity of the subject whose experience one is imagining, so that episodic future thought is immune to error through misidentification, whereas, when one remembers a past event, the identity of the subject is determined by one’s causal relationship to one’s past experience, so that episodic memory is not immune to error through misidentification. Others have argued that episodic memory is itself immune to error through misidentification (Hamilton 2009, 2013), but a more serious problem for these discontinuist arguments is that they presuppose the causal theory of memory: since the causal theory itself presupposes that there is a qualitative difference between remembering and imagining, the arguments appear to beg the question against the continuist view of mental time travel (Michaelian 2016a).