Does Participation Matter? An Inconsistency in Parfit's Moral Mathematics

Consequentialists typically think that the moral quality of one's conduct depends on the difference one makes. But consequentialists may also think that even if one is not making a difference, the moral quality of one's conduct can still be affected by whether one is participating (even if only ineffectually, or redundantly) in an endeavour that does make a difference. Derek Parfit discusses this issue – the moral significance of what I call ‘participation’ – in the chapter of Reasons and Persons that he devotes to what he calls ‘moral mathematics’. In my paper, I expose an inconsistency in Parfit's discussion of moral mathematics by showing how it gives conflicting answers to the question of whether participation matters. I conclude by showing how an appreciation of Parfit's error sheds some light on consequentialist thought generally, and on the debate between act- and rule-consequentialists specifically.