Abstract

In _On What Matters_ Derek Parfit adopts Henry Sidgwick’s idea of a duality of practical reason consisting in there being personal reasons to care about our own well-being as well as moral reasons to care about everyone else’s well-being. But this sits ill with his well-known claim in _Reasons and Persons_ that personal identity is not what matters. For this implies that were we to divide into two individuals, we would have the same reasons to care about these individuals as ourselves, though they are distinct from us. It is suggested that this is because we empathize with them in the same way as with ourselves in the future, ‘from the inside’, and that considerations of justice do not apply to them because their wills are too dependent on our wills.