It may be that everything we do is determined by some grand unified theory. If that theory has determined that we shall die by hanging, then we shall not drown. But you would have to be awfully sure that you were destined for the gallows to put to sea in a small boat during a storm. I have noticed that even people who claim that everything is predestined and that we can do nothing to change it look before they cross the road. Maybe it’s just that those who don’t look don’t survive to tell the tale.

Stephen Hawking (1942-2018) English physicist, author

“Is Everything Determined?” lecture, Sigma Club Seminar, Cambridge University (1990-04)
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Reprinted in Black Holes and Baby Universes, and Other Essays, ch. 12 (1994). Hawking's thesis that the universe is actually deterministic, but too complex to be predictable, so acting as though free will exists is useful socially and, like fluid dynamics equations, satisfactory for most purposes.