Daniel asked:

Would a deterministic universe still be determined if the inhabitants could act upon foreknowledge of future predetermined events?

For example: John is crushed to find out his universe is deterministic, he was a firm believer of free will. So using knowledge of the laws of nature and causality he constructs a Laplace demon… assuming that’s possible.

From there he uses it to learn that on Tuesday he’ll order a pizza and it’ll arrive at 8 o’clock and at 8:15 he’ll choke on the slice he was eating and die.

Could John in a determined universe act upon this foreknowledge and decide not to order the pizza? Would foreknowledge of future events and consequences endow John with free will and choice that didn’t previously exist? If not, what could compel him to order the pizza aside from relying on the metaphysical and the supernatural?

Answer by Jurgen Lawrenz

You’ve already answered your own question. If metaphysics and the supernatural don’t do the job, then there is no question.

But I may not be the best authority here. For certainty on this issue, your best bet would be to consult a clairvoyant or tarot card reader. They’re experts; and what they don’t know a philosopher could not conceivably pretend to explain.

Apart from this I think you are very confused about determinism. You’re really speaking about pre-determination or fatedness. Like: I set my alarm clock tonight to wake me up at 8 am. Circumstances may arise of which I know nothing that may present the clock from buzzing, but in every other respect I have pre-determined the fate of that clock. It must ring at the appointed time. Or else that somewhere in the universe ‘all is written’ and we are just playing out the script.

But my life is not pre-determined. I’m not a clock and metaphysical entities don’t write books.

But even if I were to believe that my will is determined (not pre-determined) by the momentary chemical conditions in my brain, it is impossible to have foreknowledge of them even a quarter of a second beforehand. This is because the chemical activity is contingent on about a million other circumstances that are active at that moment, which in turn depend on a million contingent circumstances before, and so it goes on. Laplace’s demon would go mad just keeping track of mine, let alone the rest of my family or the universe.

Anyway, he died, didn’t you know?

Some time around 1860 the thermodynamic revolution withdrew his commission. After this he became unemployable and about 30-40 years later Maxwell Clerk buried him for good.

But I’ll leave you the pleasure of discovering that story yourself.