I found the discussion of free will and determinism toward the end of the interview with Agustin Rayo to be very interesting. At one point in the discussion, Professor Rayo draws a distinction between what someone will do and what someone must do, saying that knowing what someone will do implies you know how they will exercise their free will, while knowing what someone must do implies that the action is compulsory. While describing this example, he goes as far as to say that it doesn't matter how deterministic a system is, as physics doesn't concern what must happen, only what will happen, meaning physics determines nothing about free will. While I think this is an interesting perspective, I wonder if in a fully deterministic system, is there any difference between what will happen and what must happen? If past events determine present events and since the system is deterministic, there can only be one correct set of present events, then the present events from a past perspective "must" happen, or from a present perspective had to have happened based on what events occurred prior. I would have liked to ask Professor Rayo about this perspective to hear his opinion.