I promised a while back to write a post on a topic of your choosing, in exchange for a $30 donation to my DonorsChoose challenge. I’ve got a fair number of requests, and I should really start paying them off. The first one comes from Ewan McNay, who aks:
what quantum mechanics can tell us about the existence of free will (if anything)
Oh, sure. Stick me with the tough questions.
This will be somewhat rambling and discursive, because it’s not really an area that I’ve thought much about, or where I know anything solid about the science. In fact, my first thought on hearing the question has more to do with literature than physics…
In Guy Gavriel Kay’s Fionavar Tapestry books, there’s a lot made of the Wild Hunt, a collection of “shadowy kings on shadowy horses” who not even the gods can constrain. In the final volume, helpfully excerpted here, their purpose is explained:
the Hunt was placed in the Tapestry to be wild in the truest sense, to lay down an uncontrolled thread for the freedom of the Children who came after. And so did the Weaver lay a constraint upon himself, that not even he, shuttling at the Loom of Worlds, may preordain and shape exactly what is to be. We who came after . . . we have such choices as we have, some freedom to shape our own destinies, because of that wild thread of Owein and the Hunt slipping across the Loom, warp and then weft, in turn and at times. They are there . . . precisely to be wild, to cut across the Weaver’s measured will. To be random, and so enable us to be.
To the extent that quantum mechanics has anything to say about free will, I think it’s probably in this poetic, metaphorical sort of sense. Quantum mechanics contains an element of randomness, whether you believe that observation collapses the wavefunction or that we only perceive one part of a moe complex unitarily evolving wavefunction. The world that we see is not perfectly deterministic, and causes can have unexpected effects– if you run the same experiment multiple times, under identical circumstances, you’ll see a set of different results, with the distribution of results following some probability distribution.
In a sense, then, you could say that like the Hunt in the Fionavar books, this randomness enables free will. To the extent that consciousness can be considered a quantum process (and there’s got to be at least some element of that, though I think Penrose goes a little too far), it’s possible for us to think thoughts and take actions that are not perfectly and absolutely determined by the history leading up to those events. And that’s really the essence of free will.
Of course, the whole business of “consciousness” is so murky that it’s difficult to say anything really sensible about it. There really isn’t much solid science regarding consciousness, even from people who say they know what’s going on, and it’s difficult to say anything scientific about free will without it. So any attempts to tie QM into free will are necessarily going to be kind of muddled and unscientific.
On a metaphorical level, though, I really like the Fionavar thing, so I’ll go with that.