A morally responsible agent is someone who is properly subject to the demands, expectations and evaluations of morality. In practice, we subject only normal human adults to these expectations and evaluations. We exempt non-human animals, inanimate objects and the insane from them and we subject children to them only to a limited degree (a degree that increases, of course, as they grow older). While praise and blame are not restricted to agents who are morally responsible, only morally responsible agents merit praise or blame for their actions. It may be appropriate or useful to praise and blame (or reward and punish) agents who are not morally responsible – for example as a means to controlling or altering their behaviour or dispositions. But such attitudes and treatment are not merited or deserved by these agents. Only morally responsible agents merit praise and blame for what they do. The task of a philosophical account of moral responsibility is to explain why some agents merit praise and blame for their actions. To execute this task is to identify the criteria for inclusion in the moral community.

There is no expression in Classical or Hellenistic Greek that corresponds to the English expression ‘moral responsibility’. However, the topic of moral responsibility was the subject of lively discussion and debate in the Classical and Hellenistic periods. For it was generally agreed by all major figures and schools that agents whose activity is properly evaluated in moral terms – that is, as virtuous or vicious – are distinguished by possessing the capacity of reason.