You Don't Have Free Will

March 18, 2012
You Don't Have Free Will


By Jerry A. Coyne

The term "free will" has so many diverse connotations that I'm obliged to define it before I explain why we don't have it. I construe free will the way I think most people do: At the moment when you have to decide among alternatives, you have free will if you could have chosen otherwise. To put it more technically, if you could rerun the tape of your life up to the moment you make a choice, with every aspect of the universe configured identically, free will means that your choice could have been different.

Although we can't really rerun that tape, this sort of free will is ruled out, simply and decisively, by the laws of physics. Your brain and body, the vehicles that make "choices," are composed of molecules, and the arrangement of those molecules is entirely determined by your genes and your environment. Your decisions result from molecular-based electrical impulses and chemical substances transmitted from one brain cell to another. These molecules must obey the laws of physics, so the outputs of our brain—our "choices"—are dictated by those laws. (It's possible, though improbable, that the indeterminacy of quantum physics may tweak behavior a bit, but such random effects can't be part of free will.) And deliberating about your choices in advance doesn't help matters, for that deliberation also reflects brain activity that must obey physical laws.

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