In an episode of the sitcom Taxi, cab driver Jim Ignatowski (Christopher Lloyd) has a dream in which he foresees a series of increasingly unlikely events culminating in the death of fellow driver Alex Rieger (Judd Hirsch). The last part of the prophecy has Rieger in his apartment wearing a green shirt and a catcher’s mask and dancing the Can-Can when at exactly seven o’clock there comes a knock at the door and on the other side is death. Even as the events start coming true, Alex dismisses Jim’s dream as superstition, so much so that he intentionally puts on a green shirt and a catcher’s mask and starts dancing the Can-Can. As he is doing this the clock strikes seven, there is a knock at the door, he opens it and…well, just watch. It’s pretty funny.
The joke turns on our intuitions about free will. The dance Rieger does at around 2:29 in the clip above is a complex activity. It cannot be performed without volition and intent. If you truly believed that dancing the Can-Can while wearing a green shirt and a catcher’s mask would cause you to die you simply wouldn’t do it. No one could make you. (Well, someone could put a gun to your head, but at that point it would no longer be clear how best to avoid death.) Some actions can only be performed voluntarily.
In his book Freedom Evolves, Daniel Dennett puts forward arguments against free will and in favor of hard determinism. Or, more specifically, Dennett argues that hard determinism is compatible with the only notion of free will that he finds coherent, and so he leans toward hard determinism to prove his point. It’s worth reading, but you can also watch this talk from 2003 in which Dennett hits the highlights. It’s basically the movie version of the book.
Dennett believes that consciousness is biochemical phenomenon. There is no ghost in the machine, no more than a beaker full of chemicals has a soul. Free will is an illusion created by the unpredictable nature of human brains and the implacable human desire to feel special. Dennett takes aim at two pro-free will positions that I call the complexity argument and the morality argument.
The complexity argument holds that human behavior is so complicated that it is strange to imagine it arising from purely deterministic physical systems. Dennett answers that this underestimates the complexity of physical systems, in particular animals shaped by a long process of natural selection. An interesting counterexample he cites is Conway’s Game of Life, the computer program in which a simple algorithm for setting and resetting points on a grid gives rise to astonishingly beautiful and dynamic patterns. If a handful of mathematical rules can give rise to puffers, rakes and glider guns just think what evolution can do.
The morality argument hinges on the discomfort many people feel in imagining a physical basis for consciousness. If our deepest selves are the result of neural activity, we are just machines, no better than a lawnmower or a blender, and if this is true morality goes out the window. You can’t throw someone in jail for murder if their brain made them do it. But here again Dennett claims that we are underestimating nature’s sophistication. Suppose we really are machines whose moral behavior is “just” a mechanical response to stimuli. Consider all the stimuli that would go into making a moral decision. There would be visual and aural input from the people around you, memories of instruction from your parents, any inherent capacity for empathy wired into your brain, and so forth. A complete survey of all the purely mechanical inputs that could steer a moral golem would end up indistinguishable from what would shape behavior in a conventional notion of morality. You end up recreating all the elements of what Dennett calls “the varieties of free will worth having.”
I am sympathetic to both of Dennett’s responses, but still have trouble with hard determinism. It arises not from a sense of unease but from a basic thought experiment that I don’t think he addresses, but which is alluded to by that episode of Taxi.
If determinism is true, given sufficient information about the current state of the universe it would be possible to predict future states of the universe with complete certainty. Or maybe not complete certainty, but say we have a supercomputer that can predict the events of the next hour with 99% accuracy. So we fire it up and it tells us that at exactly seven o’clock this evening I will put on a green shirt and a catcher’s mask and start to dance the Can-Can. This isn’t a matter of life and death, but nevertheless I am determined not to do it, if only to prove Daniel Dennett wrong. But say he’s right: what happens as seven o’clock approaches? Will a heretofore unnoticed catcher’s mask fall off a high shelf and land smack dab on my head? Will my limbs start to dance the Can-Can of their own accord as I look on in horror? All possibilities seem absurd. So absurd that this thought experiment seems like a reducto argument against hard determinism, in the same way that time travel seems like an impossibility once I consider a scenario in which I kill one of my ancestors. Crucially, this argument is convincing even if you share Dennett’s intuition about a purely physical basis for consciousness.
You can be completely untroubled by determinism and still think it’s impossible.