Of all the age-old questions of philosophy, the problem of free will might be most likely to result in existential angst. In this video from Wi-Phi or Wireless Philosophy, the English philosopher Richard Holton, formerly of the Massachusetts Institute of Technology and now at the University of Cambridge, outlines the two problems often used to argue that free will doesn’t exist. The first says that, if the laws of physics are fixed, all our choices must be predetermined. The second holds that, with enough computing power and knowledge about how the Universe works, someone could theoretically peer into the future to see the predestined outcomes of our lives – which would also mean we’re not free. However, using a clever thought experiment, Holton demonstrates how the second conclusion doesn’t necessarily follow from the first. That is, our ‘books of life’ can never truly be foreknown, except by a thinker who exists entirely outside physics itself.