Time-Travel, Causation, and the Direction of Time

Abstract

In this thesis I combine a definition of time-travel with issues in the philosophy of the direction of time and causation. I undertake some conceptual analysis of the notion of time-travel and I then ask what implications about time we must accept given the definition of time-travel that I have proposed. I then offer a new way of representing the taxonomy of views on time, and I argue that A-theoretic views (which I define as those that are realist about the moving present) are incoherent. In doing so, I pay particular attention to McTaggart’s paradox and some analogues of it. Furthermore, I show that A-theoretic views are incompatible with my definition of time-travel, and that the problematic feature is the A-theorists’ commitments surrounding the ordering of time, and the moving present. I show that it is the A- versus B-theoretic dispute, and not the Eternalist versus Presentist dispute, that is most relevant to time-travel debates. This leads me to a discussion on the philosophy of the direction of time. I argue that there is no way to objectively pick out one of the two directions in time as the privileged direction of time, and that the direction of time is given by convention only. I reject the thermodynamic/entropic account of the direction of time, and endorse a causal account on which the direction of time and the direction of causation cannot come apart. Additionally, I appeal to psychological features of agents in time (such as memory accumulation) to account for the assignment of a direction to time, and for the experience of a passage of time. I then show that direction of time plays a crucial role in time-travel stories, and that on my combination of a causal theory with a psychological or memory accumulation theory we can give a tidy account of what is happening with time in time-travel stories.