Abstract

Is it possible to change the past—to make something that has happened not have happened? Past-alteration is widely believed to be ‘logically impossible’. But despite this, there have been few attempts to actually apply logical resources to the question of whether it is possible to change the past. This chapter articulates a novel tense logic and uses it to argue that past-alteration is possible—with just a single dimension of time—so long as it’s possible for time to have a certain kind of structure: one which is ‘backwards-branching’ and in which the relation of precedence ‘comes apart’ from the relation of succession. The remainder of the chapter explores some of the metaphysical implications of this account of what it is to change the past.