Here’s an interesting asymmetry between reasoning under moral uncertainty and reasoning under factual uncertainty. Or, at least, an interesting prima facie asymmetry, since there might be a simple explanation once we set everything out clearly.

The followinig situation is reasonably common in reasoning under uncertainty. We have three choices, A B and C. Which of these is best to do depends on whether p or q is true, and we’re certain that exactly one of them is true. If p is true, the best outcome will arise from doing A. If q is true, the best outcome will arise from doing C. Yet despite this, the thing to do is B.

Here’s an example. I’m in Vegas, thinking about betting on a (playoff) football game. The teams seem fairly even, and there is no points spread. As usual, to bet on a team I have to risk $55 to win $100. Fortunately, I have $55 in my pocket. Let A = I bet on the home team, C = I bet on the away team, and B = I keep my money in my pocket. Let p = the home team wins, and q = the away team wins. (Given it’s a playoff game, we can be practically certain that one of these is true.) So if p, I’ll be best off if A, and if q, I’ll be best off if C. Still, the thing to do is B, since both A and C have negative expected value.

Now the puzzle is that this kind of situation doesn’t seem to arise for moral uncertainty.

Let p and q be fundamental moral theories such that we are certain exactly one of them is true. For example, let p be the proposition that a particular kind of consequentialism is true, and q be the proposition that a particular deontological theory is true. And imagine we are certain that one of these is true. (If this is implausible, use more than 2 moral theories here so we have enough cases that we can be confident in practice that one of them is the true one.)

In this case it is much harder to find examples where the the thing to do is to select the option that is sub-optimal according to all the live theories. Let A be an act that maximises utility while violating lots and lots of people’s rights, so it is best according to consequentialism. And let C be an act that performs all your duties and violates no rights, but produces very little utility. In the middle, let B be an action that only violates a few rights, and produces almost as much utility as A. It doesn’t seem that B should be done, even if it seems that B is close to being the best action by both theories.

Here’s what I think the explanation of the asymmetry is. (This is actually as much Ishani’s explanation as mine.) In the football case, what is true is that if the home team will win, the best outcome will come from betting on it. But a ‘narrow scope’ normative claim, like “If the home team will win, I should bet on it” is not true, and doesn’t follow from this fact. We can prove this conditional is false because in the (nearby!) possible world/epistemic possibility where the antecedent is true, the consequent is still false. I shouldn’t bet on the home team because that has negative expected itility, and I shouldn’t do things with negative expected utility.

In the moral case, the ‘narrow scope’ normative claims are true. If consequentialism is true, then I should do A, where the ‘should’ here has narrow scope. (That is, it is an unconditional normative claim, made conditionally on the truth of some moral theory.) And if the deontological theory is true, then I should do C. Since (by hypothesis) one of these two is true, I should do A or C. We can’t make this kind of inference in the factual uncertainty case because the narrow scope conditionals are not available. And this explains the asymmetry.