(Dr. Alasdair Richmond) In this module we'll think about some issues in metaphysics, a branch of philosophy that investigates the ways that reality could intelligibly be. Our case study will be the possibility, or otherwise, of time-travel. Some have thought that the apparent possibility of creating a machine that we could use to transport a person backwards in time can be ruled out just by thinking about it. But is time-travel really logically impossible? What would the universe have to be like for it to be possible? And can we know whether our universe fits the bill?