Suppose you think the Humean doesn’t make enough sense of the feeling that there’s something specially bad about not doing what you know is right, or doing what you know is wrong. Then you might try combining moral internalism with the opposite of Ordinary Jo’s view of desires. What would that give you? On some plausible interpretations, this is Aristotle’s view:
The idea here will be that there are some things which it’s right to want, and some things which it’s wrong to want. (So it might be right to want to help people, for example, and wrong to want to torture a cat.) Wanting something you shouldn’t want will be a bit like believing something you shouldn’t believe (something false, for example: you shouldn’t believe that the Earth is flat). You might say: ‘Wanting something to be done is a bit like thinking it’s right’.
Because the Aristotelian disagrees with Ordinary Jo about desires, she can agree with Ordinary Jo about morality: ‘There are moral truths’ (so, as long as they’re not too difficult to work out, there can be moral knowledge).
The Aristotelian view of akrasia states that if you know something is right and fail to do it, or know something is wrong and do it anyway, then you have something like a contradiction between your beliefs (as if you both think something is right and think it is not right at the same time—like thinking that a pen is red and that it’s not red at the same time).
Yes, it’s irrational in the same way as it’s irrational to have contradictory beliefs. Is this the kind of irrationality which is involved in akrasia – in failing to do what you know to be right, or doing what you know to be wrong?