Why do people do acts that are agreeable or useful to other people and why do evaluators approve of such acts, and even approve of acts agreeable or useful to the actor herself?

As it is part of the moral sceptic’s undertaking to show that ethical motivation can be understood ‘outside of ethics’ as it were, the answers to these questions will have to be in terms other than duty or rightness. For the natural virtues, whatever characteristics or traits they may turn out to be, the dispositions to perform and to approve are natural — some sort of original instinct, primary impulse or genetically imprinted drive. However it is clearly of more interest, indeed more difficult, for the sceptic to offer an explanation of those instances where the motivation to act and to approve cannot directly be attributed to any natural or instinctive or genetic impulse. An obvious candidate in need of such an explanation is the action done because it is ‘just’.

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