Although I agree with Professor Henderson (Reference Henderson2005) that we should acknowledge that many psychiatric patients have a greater degree of volition, or free will, and hence of moral responsibility, than they are often considered to have, I think that he has made things far too easy for himself.

Professor Henderson has simply assumed that we have free will, at the same time maintaining that ‘as brain function comes to be increasingly understood, it is possible that abnormal behaviour will be attributed less to the person's power of choice in regard to action, and more to abnormalities of brain function or genotype’. Both these assumptions are not uncontroversial and would deserve at least some arguments to lend them plausibility. One of many questions which arise here is ‘why should only abnormal behaviours be attributed less to the person's power of choice in regard to action and more to abnormal brain function?’ Could not normal behaviour equally be attributed less to the free will of the agent and more to normal brain function as we come to understand brain function better? Henderson has given us no reason to think that this could not be the case with normal behaviour as well.

Interestingly Henderson cites Libet et al (Reference Libet, Freeman and Sutherland1999) but curiously omits to mention Libet's famous discovery of a readiness potential arising in the brain some 350 ms before a conscious decision to act is experienced. This finding is usually interpreted as evidence of unconscious initiation of the volitional process, and hence as evidence against freedom of the will. Henderson also quotes Alper (Reference Alper1998): ‘Even if human beings are genetically deterministic systems, their behaviour may still be unpredictable and they may still possess free will’. But if our behaviour is unpredictable or random, then we do not have free will, because free will implies that we are autonomous agents who can bring about our actions intentionally.