Here’s the summary of the argument (links added by me for context):
I hope to advance this debate with an argument that uses recent empirical results against the Doctrine of Double Effect as Greene and Singer wish to, but which avoids the problems Berker notes, and which better fits the data. It runs as follows:
[Unequal Vividness Explanation] Double Effect is accepted because of how unequally vivid representations of actions’ intended and merely foreseen consequences affect our desires.
[Unreliability Claim] When the effects of unequally vivid representations upon our desires are decisive in causing our judgments about what to do, we are usually mistaken.
[Conclusion] In accepting Double Effect, we are likely to be mistaken.
Full paper here. What’s cool about this is that the unreliability claim, as I understand it, rests on both a descriptive claim (in practical judgment, unequal vividness frequently leads to error) and a normative claim (error in practical judgment is likely to constitute error in moral judgment). So I don’t think Neil is trying to derive an is from an ought. But at the same time, the normative claim in question is extremely modest, and one that most people involved in the dispute in question should be able to accept. The method he’s using, then, seems capable of using neuroscience to make progress in previously intractable disputes like this without falling victim, as Greene does, to errors that Hume was pointing out three centuries ago.
Unequal vividness also seems like a promising way of deflating other deontological hobby-horses, like the causing/allowing harm distinction. Surely one reason that we’re less willing to condemn someone for failing to donate $10 to UNICEF, even with the knowledge that the donation will likely save a child’s life, than we are to condemn someone who runs over a child with his car and then keeps going is that the latter scenario is far more vivid.