  To the extent that impressions are involuntary, Marcus’ ‘erase’ may mean ‘override’. He may be saying: for the purposes of action and response, wipe out the influence of such-and-such impressions (Plato’s Protagoras, similarly, speaks of rendering the power of appearance unauthoritative [356e]); focus instead on your understanding of the whole, which will give you a different impression. However, the Stoics’ image of the mind as a wax tablet being impressed by different shapes gives a particular point to talk of ‘erasing.’ The work Marcus is doing is to replace an inadequate impression with another impression, this one better grounded in a comprehension of reality. Perhaps making the second mark requires erasing the first—or perhaps making the second mark is a means of erasing the first, for it may be that the withholding of assent from compelling impressions requires countering them with others.