You are quite right. There seems no good reason why genetic causes should absolve us from moral responsibility any more that other causes of our behaviour. This is a point that has often been made by Richard Dawkins. If there is a threat to free will and moral responsibility, it is determinism per se, not genetic determinism in particular. Of course, there remains the question of whether determinism does undermine free will and moral responsibility. Compatibilists say no--they say you are free as long as your actions issue from your own conscious choices, even if those choices themselves are determined by your genes and environment. Incompatibilists say yes--if your actions are ultimately determined by causes beyond your control, then you aren't free, even if the determination proceeds via your conscious choices. But, either way, genetic causes have no special status. Compatibilists will say that genetic causes, like other causes, don't undermine your freedom when they influence your...

On views of morality that I find plausible, your virus wouldn't stop us judging that certain things (cheating, inequity . . .) are wrong, even though it would probably mean that we were not longer motivated to avoid them. (But on other 'non-cognitivist' views, which tie moral judgements to our motivations, this would mean that we would cease even to judge that those things are wrong.) A loss of emotional reactions is likely to undermine more than just moral motivation. In his book 'Descartes' Error' Anthony Damasio argues that without emotional reactions there would be no effective decision-making of any kind. Damasio describes a patient with severe damage to his prefrontal lobes. This patient could see the pros and cons of alternative courses of action (such as Tuesday versus Wednesday for his next appointment) but would discuss the options interminably without ever reaching a decision. This suggests that emotional reactions to envisaged situations are an essential part of the mechanism...