We spend much of our adult lives thinking and reminiscing about particular events of the past, which, by their very nature, can never be repeated. What is involved in a capacity to think thoughts of this kind? In this paper, I propose that such thoughts are essentially connected with a capacity to communicate about past events, and specifically in the special way in which events of the past are valued and shared in our relationships with one another. I motivate this proposal by way of the claim that such thoughts are practically useless: there are no practical, forward-looking tasks that require information which is specific to particular past events. Thus I suggest that thoughts of this specific kind have a home only in the cognitive economy of a creature who finds past events to be of interest for their own sake, and that this interest in the past is a peculiar feature of human social life.