Sigh. Well, I suppose I'd feel remiss if I didn't say something on this topic...
The course I'm involved with teaching at the moment has students consider the following case:
http://www.medicalnewstoday.com/articles/4022.php
Or, for those who can't be bothered following the link, it is basically a case of the presence and absence of pedophilia covarying with the presence and absence of a tumor.
They need to consider whether or not the man is morally responsible for his pedophiliac actions according to (their interpretation of) Aristotle's theory of moral responsibility. This is important (in part) because Aristotle's theory has been extremely influential on the legal notion of moral responsibility in western legal settings; his theory seems to accord with our own intuitions reasonably well; and his theory kind of attempts to deal with a serious objection to the effect that nobody is morally responsible (praiseworthy or blameworthy) for anything they do.
Aristotle's theory is (roughly) that we are morally responsible for actions that aren't involuntary. Involuntary actions are actions that are done in certain kinds of ignorance (e.g., of particular details of the action etc) or actions that are due to external force. (I could go on but I won't).
Problem for Aristotle's theory: Suppose that our beliefs and desires are caused (which is to say 'forced') by things outside our control - such as by our genes or by our parents (who we surely didn't choose to be born to) or our environment (which we surely didn't choose to be placed in). Then it seems that all our actions are the result of force which is to say they are involuntary which is to say that nobody is morally responsible (praiseworthy / blameworthy) for anything they do.
What enables us to say that this man is not morally responsible for his behavior because his behavior was caused by forces outside his control (his tumor / the state of his brain) while simultaneously enabling us to say that other adult humans are morally responsible for their behavior even when their behavior is caused by forces outside their control (the state of their brain)?
Aristotle also says that while we don't choose ends / desires (what seems good to us) we deliberate on different options that are means to our ends. He thinks that deliberative actions form a subset of voluntary actions. Since some people clearly do have the capacity to deliberate and deliberative actions are a subset of voluntary actions (for Aristotle) it thus seems that some people do have the capacity for voluntary action.
He seems correct that the capacity for rationality is something that accords with our intuitions around whether an agent is or is not morally responsible. Adult humans are paradigmatically deliberative and morally responsible; animals, infants, people with certain kinds of intellectual handicap / mental disorder / disease paradigmatically are not.
But it seems that we don't choose to have the capacity to deliberate, rather that is something that is forced on us... But then we do in fact hold people morally responsible for some of their actions (praise / blame) and excuse them for others so we need to say something about where we draw the line.
Oh, what a puzzle...
IMHO:
- Deliberative capacity works well to delimit the scope of moral responsibility. Tough **** that we didn't deliberately choose to be born with a deliberative capacity - simply having it is enough to make us morally responsible agents.
- There are issues around whether the tumor altered the apparent good (what seemed desirable e.g., having sex with children) vs altering the rational capacity (ability to inhibit acting the way he did). That might make a difference...
- EITHER: Control isn't required for moral responsibility (merely having a deliberative capacity is enough) OR: Even though nobody is morally responsible (in the sense that their acts are ultimately caused by things outside their control / force) we are still justified in holding people to be morally responsible for some of their actions. I think this is ultimately a linguistic decision and there isn't much of a substantive difference between those options)
- Whether the universe is deterministic (A predicts B with 100% accuracy) or whether there are irreducible quantum indeterminicies (A predicts B to 0.5, A predicts C to 0.25, A predicts D to 0.25) things are ultimately determined (or the probabilities are fixed) by things outside our control. We still have reason to hold people morally responsible, however. Firstly because it impacts on their future offending (preventing it) and secondly because it impacts on others offending (modelling). People often have this intuitive distinction between law being about 'evil' where people should be 'punished' in a retributive fashion whereas psychiatry being about 'illness' where people should be 'rehabilitated' where we have pity / compassion for them. Personally... I think this distinction should be broken down. Not to say that the mentally ill should be treated as criminals, but rather that criminals should be rehabilitated too. Not that there are enough resources to rehabilitate the legally insane... But that is my ideology, anyway...