Does freedom bubble up from the quantum realm?
I’ve been writing lately (in this article and blogpost, for example) about agency and more specifically about whether neuroscience or basic physics rule out the idea of free will, of organisms like us being able to genuinely make choices based on their own reasons and thus act as causal agents in the world. I’m grateful to Philip Goff for responding to some of these ideas in a recent blogpost and to Philip Ball for continuing the conversation in a post of his own.
I respond to their arguments here and make some more general points along the way. (For convenience, I will refer to the two Philips by their last names, which feels a bit rude, so, sorry, Philips!).
The question that Goff takes up is my claim that fundamental indeterminacy at the quantum level creates some room in which free will can operate. He quotes the following passage, which sums up the argument:
“The inherent indeterminacy of physical systems means that any given arrangement of atoms in your brain right at this second, will not lead, inevitably, to only one possible specific subsequent state of the brain. Instead, multiple future states are possible, meaning multiple future actions are possible. The outcome is not determined merely by the positions of all the atoms, their lower-order properties of energy, charge, mass, and momentum, and the fundamental forces of physics. What then does determine the next state? What settles the matter?”
To be clear, this line of thinking does not originate with me. It’s been well explicated by people like George Ellis and Helen Steward in recent times, but really dates back to the ancient Greeks, most notably Epicurus (some of whose work was effectively reproduced by the Roman philosopher Lucretius, in the form of his didactic poem De Rerum Natura (On the Nature of Things)).
One of the most important arguments that Epicurus makes invokes what is now known as “the swerve”. Epicurus inherited from Democritus and his followers the remarkably prescient idea that all matter was composed of simple particles (which Democritus had called “atoms”) and that complicated stuff was made of different combinations of such atoms. But he objected to the rigidly deterministic laws that Democritus had developed to explain how atoms move and what happens when they collide. He famously argued that if there were no element of randomness in the movements of atoms – if they did not occasionally “swerve” – then, first of all, the universe would not exist (which feels like a biggie), and, secondly, that humans, or any animal, would be incapable of autonomous action or real choice.
In modern parlance, if we are made of atoms and their movements are entirely determined by the low-level laws of physics, then the atoms are gonna do what the atoms are gonna do. It doesn’t matter what we want – indeed, wanting would never arise – why would it? Alternate possibilities would simply not exist. Everything would be determined in an unbroken line from the beginning of the universe to the end of time.
The swerve – that element of randomness – breaks that chain and introduces freedom and indeterminacy into the universe. It creates possibilities where none would exist without it. But Epicurus’ target was not just determinism – he also argued forcefully against reductionism, the idea that the origins of causal power, even in complex systems like living organisms, are ultimately entirely traceable to the forces controlling the movements of atoms. He recognised that this idea is incompatible with the autonomy of living beings, including humans.
His argument (and mine) is thus not simply that the world has some randomness in it. Many people rightly point out that randomness by itself does not provide free will. The argument goes that if my decisions are fully pre-determined by the laws of physics, then they are not freely made by me. But if they are determined, in the act of making a decision, by random swerves of atoms in my brain, then they are also not freely made by me.
This is true, but it ignores Epicurus’ wider point – that the existence of some randomness at the lowest levels means that causality does not fully inhere at those levels. Instead, the higher-order configuration of a system can play a causal role in its evolution from state to state. (In other words, when determinism falls, reductionism falls with it).
This is the argument I have been making too, updated with reference to our modern understanding of fundamental physics (and neuroscience, genetics, and evolution). Epicurus’ swerve has a modern echo in the indeterminacy inherent in quantum theory and empirically observed in events at quantum levels. (Though there are multiple different interpretations of what the quantum theory means for the ultimate nature of reality).
The question that Goff and Ball take up is whether this quantum indeterminacy really leaves room for or rescues free will. (As an aside, I don’t think free will needs “rescuing” – the fact that we make decisions is one of the most basic aspects of our experience. It’s what we do all day, every day – go around making one choice after another. Any claim that this deepest aspect of the phenomenology of our existence is an illusion should in my view carry a heavy burden of proof).
Goff takes this indeterminacy (and my position of incompatibilism) for granted for argument’s sake, but says:
“It sounds intuitive, but I don’t think this strategy ultimately works. Even among indeterministic interpretations of quantum mechanics, although the physics doesn’t conclusively settle what will happen, it does determine the objective probability of what will result from any given physical circumstance. Although we can’t predict with certainty, say, where a given particle will be located when we make a measurement, the Born rule tells us, for any given location in the universe, precisely how likely we are to find the particle in that location. It’s not determinism, but it’s not a ‘free for all.’”
He goes on to imagine a scenario where the Born rule plays a role in determining the “objective probability” of his own macroscopic actions:
“Mitchell worries that if the physics determines what I’m going to do, then I’m not really free. But physics determining the objective probability of what I will do is no less constraining. If whether I water Susan (my Madagascan dragon tree) is really up to me – in the strong incompatibilist sense – then surely the physics can’t fix how likely it is that I will water Susan. If it’s just totally up to me, then it could go either way depending on my radically free choice.
Here’s a little thought experiment to make the point clear. Take the moment when I’m about to decide whether or not to water Susan. Let’s say the Born rule determines that there’s a 90% chance my particles will be located in the way they would be if I watered Susan and a 10% chance there’ll be located in the way that corresponds to not watering Susan (obviously this is a ludicrously over-simplistic example, but it serves to make the point). Now imagine someone duplicated me a million times and waited to see what those million physical duplicates would decide to do. The physics tells us that approximately 900,000 of the duplicates will water Susan and approximately 100,000 of them will not. If we ran the experiment many times, each time creating a million more duplicates and waiting for them to decide, the physics tells us we would get roughly the same frequencies each time. But if what happens is totally up to each duplicate – in the radical incompatibilist sense – then there ought to be no such predictable frequency. The number that do and don’t water the plant should change each time, as the radically free choices of each individual varies.”
My first reaction to this is similar to the main point that Ball makes in his own commentary – namely, that it is an ill-posed thought experiment. The Born rule applies to quantum events and elementary particles, not to macroscopic objects and certainly not to the decision-making of agents. Moreover, it applies independently to single particles and events (unless they are entangled). So, in a complex system, all those probabilities will multiply exponentially to create a massive web of indeterminacy.
This is the main point of my argument. The quantum events do not decide the outcome – they merely make the whole system indeterminate. This has two key implications: the next state of the system is NOT determined by the current state plus the laws of physics. And the causal influences are NOT restricted to the lowest level of the system.
I also do not see what the idea of “objective” probabilities of various outcomes being determined by physics is doing in this argument. The whole idea of probability is open to many different interpretations and it’s not clear at all that there is, or should be, a straightforward mapping of its meaning at the level of quantum events to its meaning at the level of human choices. These levels are simply incommensurate. As Ball says, “It’s best, I think, to explain phenomena at the conceptual/theoretical level appropriate to it.”
The important point is that possibilities exist – they don’t have to be equally likely. Indeed, it will almost always be the case that you won’t weight the choices open to you equally. I don’t think anything in particular follows from that.
Goff follows up with a broader point, which is interesting, though I’m struggling to fully grasp what he means by it:
“All is not lost, however. I think Mitchell is conflating two claims:
- The laws of physics are deterministic
- The universe as a whole is deterministic
How could these come apart? They come apart if the laws of physics are ceteris paribus laws, i.e. laws that tell us what will happen in the absence of other causal influences. On this interpretation of physical law, the probabilities yielded by the Born rule are the objective probability of what will occur in the absence of some other causal influence. Such other causal influences might include the kind of irreducible causal powers Mitchell believes reside at the level of neurobiology. Mitchell seems to be concerned to avoid a violation of the laws of physics. But if the laws of physics are ceteris paribus laws, then higher-level causal powers should be thought of as complimenting the laws of physics rather than contradicting them. If physics basically tells us ‘X will happen unless there are some higher-level causal forces,’ and X doesn’t happen precisely because there are higher-level causal forces, then nothing occurs that is inconsistent with physics.”
I think I kind of agree with this, though I might not word it like that. I do think there are other kinds of causal forces at work, which constrain and inform how the physical state of our brains evolves from moment to moment. In particular, I have argued (in this recent talk, for example, or this longer one) that what drives the next state is the meaning of the current state (or the meanings, plural, of all the sub-states across the brain), which is instantiated in the configuration of the neural circuitry and the history that it embodies.
But I would argue that such an effect or interpretation is only possible because the laws of physics are not deterministic. If they were, then the universe would be deterministic and they would not be ceteris paribus (all other things being equal) laws. There would be, indeed could be, no “other things”, from a causal perspective. (At least, that’s my strong intuition, but I’d be very interested to hear what others, especially physicists or philosophers make of the idea).
Thankfully, it seems that indeterminacy does exist (at least according to a majority interpretation of the current knowledge of physics). Epicurus was right – the atoms (or more fundamental particles) do seem to swerve every now and then. And life, agency, and yes, even what we call free will, can evolve in the causal spaces created by those swerves.
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