 The first of these questions is about whether mental imagery itself (that is not in conjunction with perception) can lead to knowledge or even to new information. Jean-Paul Sartre, for example, famously claimed that “nothing can be learned from an image that is not already known.” (Sartre 1948, 12) Since on his view “it is impossible to find in the image anything more than what was put into it,” we can conclude that “the image teaches nothing.” (Sartre 1948, 146–7). Sartre was not always making a clear distinction between imagination and mental imagery, so it is not clear whether it is imagination or mental imagery that teaches nothing. Contemporary philosophers tend to raise this issue about imagination (Langland-Hassan 2016, 2020, see also Kind and Kung 2016), but the question from our point of view is whether it is true of mental imagery. And here some examples seem to suggest that even if imagination teaches nothing, mental imagery can and does. When you want to wrap a chocolate box in wrapping paper, you look at it and form (often involuntarily, not by counting to three and voluntarily imagining) visual imagery of the wrapping paper needed and you may find your estimation of the size of the paper unexpected or surprising. Maybe it’s larger than you had assumed. Or smaller. Your estimation of the size of the paper needed can be very different before and after forming the mental imagery of the paper covering the chocolate box (and this can, of course, be still different from the size of the paper actually needed, see Gauker forthcoming for more examples of this kind). If we can generalize from this example (see Levin 2006 for discussion), then mental imagery can lead to new information even if imagination cannot.