As a philosopher, I often find speculation about the implications of neuroscience for free will perplexing. While some neuroscientists describe free will in ways that I recognize, others, including some distinguished and thoughtful scientists, do not. Thus Benjamin Libet: If "our consciously willed acts are fully determined by natural laws that govern the activities of nerve cells in the brain," then free will is "illusory."
Most philosophers disagree.
Jerry A. Coyne
Alfred R. Mele
Michael S. Gazzaniga
Owen D. Jones
Among philosophers the main division is between compatibilists, who believe that free will is compatible with causal determinism, and incompatibilists, who believe that it is not. Almost all compatibilists think that we are free. Most are not determinists, but they believe that we would be free even if our actions are fully determined.
With the exception of those who work within a religious tradition, philosophers tend to be naturalists who see individual mental events as identical with events in our brains. When we say that a person's choice caused her action, we do not mean that she swooped in from outside nature and altered her destiny; we mean that an event in her brain caused her to act. On this view, the claim that a person chose her action does not conflict with the claim that some neural processes or states caused it; it simply redescribes it.
For compatibilists, therefore, the problem of free will is not that neuroscience reveals our choices as superfluous. It does not. Nor do compatibilists deny that our choices cause us to do things. The problem of free will for compatibilists is not to preserve a role for deliberation and choice in the face of explanations that threaten them with elimination; it is to explain how, once our minds and our choices have been thoroughly naturalized, we can provide an adequate account of human agency and freedom.
How can we reconcile the idea that our choices have scientific explanations with the idea that we are free? Determinism does not relieve us of the need to make decisions. And when we make decisions, we need some conception of the alternatives available to us. If we define an alternative as an action that is physically possible, then determinism implies that we never have more than one alternative. But since we cannot know in advance what we will choose, if we define "alternative" this way, we will never know what our alternatives are. For the purposes of deciding what to do, we need to define our alternatives more broadly: as those actions that we would perform if we chose them.
A person whose actions depend on her choices has alternatives; if she is, in addition, capable of stepping back from her existing motivations and habits and making a reasoned decision among them, then, according to compatibilists, she is free.
Whether this view provides an adequate account of free will is not a problem neuroscience can solve. Neuroscience can explain what happens in our brains: how we perceive and think, how we weigh conflicting considerations and make choices, and so forth. But the question of whether freedom and moral responsibility are compatible with free will is not a scientific one, and we should not expect scientists to answer it.
Whatever their views on the compatibility of freedom and determinism, most philosophers agree that someone can be free only if she can make a reasoned choice among various alternatives, and act on her decision; in short, only if she has the capacity for self-government.
Neuroscience can help us to understand what this capacity is and how it can be strengthened. What, for instance, determines when we engage in conscious self-regulation, and how might we ensure that we do so when we need to? If the exercise of self-government can deplete our capacity for further self-government in the short run, what exactly is depleted, and how might we compensate for its loss? Does self-government deplete our resources in the short run while strengthening them over time, like physical exercise, or does it simply weaken our ability to govern ourselves without any compensating benefit?
Neuroscience can answer those questions, and it can provide causal explanations of human action, but it can't resolve the question of whether or not such explanations are compatible with free will.
Hilary Bok is an associate professor of philosophy at the Johns Hopkins University. She is the author of Freedom and Responsibility (Princeton University Press, 1998).