Abstract

Denying the conclusion of a valid argument is not generally permissible if one suspends on one premise of the argument and believes the other premise. This can happen when one’s only critique of an argument is to undermine one premise. There is incoherence there. Here I examine how this is relevant to the debate on evolutionary debunking of our moral knowledge. I argue that one significant line of response to the debunker is unsuccessful: merely undermining the debunker’s empirical claim. It is not rational to respond this way and believe one has moral knowledge. First I present evidence that prominent critics of the debunking argument merely undermine the debunker’s empirical claim. Then I argue for two premises: merely undermining a premise can only justify a middling amount of doubt towards the premise and we should have no more doubt about the conclusion of a valid argument than we do about the premises. Implications of the argument are explored.