In the present paper, we first argue that it is critical for humans to forget; that is, to have some means of preventing out-of-date information from interfering with the recall of current information. We then argue that the primary means of accomplishing such adaptive updating of human memory is retrieval inhibition: Information that is rendered out of date by new learning becomes less retrievable, but remains at essentially full strength in memory as indexed by other measures, such as recognition and word-fragment completion. We conclude with a speculation that certain unconscious influences of prior events may, in fact, be stronger if those events were to be forgotten rather than to be remembered.