 Despite the disagreements among partisans of the theories of remembering discussed in section 4, they are, for the most part, in agreement on the point that remembering involves representations of past events. The role of representations in remembering, however, raises a number of difficult questions of its own. One such question concerns the implications of mental content externalism for memory content in particular.[2] Externalism, which has become the dominant view of the nature of mental content, holds that the content of a subject’s mental representations depends not only on his own internal states but also on his relationships to things in his external environment. For example, what one thinks when one thinks the thought that one would express by saying “water is wet” is determined in part by the chemical composition of the substance that fills the lakes and rivers and falls from the sky in the environment in which one learned to use the word “water”, namely, H2O; had one learned to use the word “water” in an environment in which something other than H2O fills the lakes and rivers and falls from the sky, then one’s thought would have been that that other substance is wet, not that H2O is wet (Putnam 1975). This much is common ground among externalists. But a subject might move from one environment to another, and externalists disagree about the contents of memories formed before such moves and retrieved after them. Pastist externalists (e.g., Boghossian 1989; Burge 1998) maintain that the past environment alone is relevant. Presentist externalists (e.g., Ludlow 1995; Tye 1998) maintain that the past and the present environments are both relevant. And futurist externalists (e.g., Stoneham 2003; Jackman 2005) maintain that the past, the present, and any future environments are all relevant. Since the arguments for and against these views have had little contact with mainstream philosophy of memory, they will not be reviewed here; for further discussion, see Bernecker (2010).