AND SOMEONE HAS TO CHECK ON THE CAT:

Then along came quantum mechanics. When physicists observed that behavior at the atomic level was fundamentally indeterminate, the universal validity of classical physics, as well as philosophical determinism came into question. Physicists recoiled at the idea that their science could no longer claim to predict all things with infinite precision. But, that's what quantum mechanics teaches us. We absolutely cannot know exactly how something will turn out before it happens.

Most physicists eventually accepted this idea as an empirical fact of measurement, but assumed that a flaw in quantum mechanics created the uncertainty. Perhaps, with further insight, some "hidden variable" could allow them to predict things with perfect certainty again.

But that never happened.

John Bell, in a famous 1964 paper, forced everyone to reconsider, both scientifically and philosophically, their support for determinism. His famous theorem, Bell's inequality, is an incredibly profound statement. This relatively simple mathematical proof, when applied to experimental results, gives us a choice: We must either give up determinism or give up the existence of an objective reality explained by science and measurable by humans with instruments. (You can read the gory details about the experiments here.)

So if experiments on quantum phenomena are reliable, then Bell concludes that determinism is false. Most physicists agree.

Essentially, quantum mechanics tells us that there are things which we cannot know about the future, things which are not predetermined but happen with some factor of chance or randomness. Although many things in the world may be predicted, everything is not predetermined, and our actions do not unfold mechanically in a manner predetermined since the very moment of the Big Bang. Free will is preserved.

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