Neuroscience accepts the overwhelming evidence that mental states depend on brain states. Is there room for a robust kind of free will where agents can act as independent causes of the brain states which in turn cause our actions. This kind of free will seems necessary if one accepts Christian tenets about morality, justice, and salvation. The problem is that our mental states are determined by the brain's physical properties. Because we cannot choose the physical properties of our brains we cannot really choose our own mental states or our actions. It is an interesting fact that this point is uncontroversial when we are talking about a patient suffering from psychosis due to a chemical imbalance in the brain but resisted when we are talking about people with normally functioning brains. What differentiates the psychotic from the mentally-healthy individual is the difference in the physical properties of their brains. The way a mentally-healthy person reasons about situations and decides what courses of action to take are just as determined by his normally-functioning brain as the psychotic's reasoning and decision-making are determined by his malfunctioning brain. This raises some interesting questions about moral responsibility. If a psychotic becomes a serial killer due to a chemical imbalance in his brain, does this exempt him from responsibility for his actions? If so, where do we draw the line for when brain states exempt someone from moral responsibility since all of our actions are ultimately determined by our brain states? Does this exempt all of us from moral responsibility?
What about the dubious arguments that quantum indeterminacy leaves room for robust free will? Quantum effects are quite negligible on the level of neurons, that overall brain function is based on large networks of neurons and thus the unpredictable behavior of a single neuron would make little difference in the brain as a whole, and the random fluctuations associated with quantum indeterminacy are minute compared to thermodynamic fluctuations or fluctuations in the blood supply to the brain. This latter point is especially poignant because even if quantum fluctuations did occur at the level of neurons their effects would be 'drowned out' by the much larger deterministic sorts of bodily fluctuations.
Rather than finding a place for free will, indeterminacy could be used to excuse a person of responsibility for his actions.
Determinism is the position that all events--including human actions--are determined by the causes that preceded them. Indeterminism holds that some events are not determined by prior causes but rather occur randomly and unpredictably with no causes at all. If any of our actions occur randomly, without cause, then those actions are not under our control. If we set up a machine to 'decide' whether or not to shoot someone based on the results of a random number generator (odds meaning shoot, evens meaning do not shoot) we would not say that the machine 'freely chose' its action or was responsible for it. For this reason we cannot use quantum indeterminacy to provide free will or assign responsibility for human actions. The emerging picture strongly implies that we cannot choose otherwise than we do whether or not determinism is true. By all indications, a robust, counter-causal sort of free will is an illusion: Either human actions are completely determined by prior causes or they occasionally occur randomly for no reason at all.
Yes, thinking is dangerous ;-)
Prins V.