Olivia Coombes is a philosopher and teacher at the University of Edinburgh whose research focuses on issues about the possibility of time travel, the paradoxes involved in time travel, and how these topics relate to the question of free-will. In addition to this, Liv is also the co-host of the Edinburgh-based podcast Two Philosophers: One Podcast, No Problems.

Since the philosopher David Lewis, and before, philosophers, scientists, movie fans (pretty much everybody), have deliberated the possibility of time travel. People have asked questions like: What is the order of time? If we could build a powerful enough machine, would we be able to travel through time? Causation goes forwards in time, but is there anything stopping it going backwards? And, if it could, can we have causal loops in time?

In this episode we’re going to be focusing on the grandfather paradox, which is one instance of the question: can time travellers change the past? This paradox asks us whether or not we could go back in time and kill our own grandfathers. Many people say no: it is logically impossible, like squaring circles, or making something from nothing. However, Olivia Coombes thinks differently. She thinks that we can kill our grandfathers, and that we are able to change the past.