Here is an ethical version of Moore's paradox, or more precisely an ethical instance of Moore's paradox:
Consider the following:
2. I am morally barred from believing that P
3. If I am aware of P, psychologically, I must (believe P or believe not P)
4. I believe not P (from 2-3)
5. Moore's paradox(from (1) and (4))
(Moore's paradox is what results from saying "P, but I don't believe it.")
The above argument holds with the assumptions (1)-(3). I do not think that they are difficult to argue for. (1) claims that some P is true. Easy enough.
(2) is a bit trickier, and may be where the weak point here is. Are there some facts that are so immoral that one should not believe in them even with evidence?
There are some beliefs X such that if you believe them you are evil. Consider a sentence of the form:
#=Members of race x are all liars in virtue of their being members of race x.Presumably believing # makes one a racist. Racism, let's say, is evil. So believing # makes you evil. One is morally barred from doing things that make one evil. So one is morally barred from believing #.
(3) is a Jamesian Epistemic-Moral Law of Excluded Middle (JEM-LEM). William James argues, I think convincingly, that as a matter of rational psychology it is impossible to be agnostic about certain things. I take it that there are #-like Ps that are susceptible to the JEM-LEM.
Hence the paradox. Here, we have a case of "P, but I am not allowed to believe it". Can this happen?
Note as an aside that if you deny (4) because you don't accept (2) then you may be committed to cases like the following:
There are also also arguments that I take seriously that claim that there is some knowledge that compel moral action in the same way that some knowledge will compel rational belief. Let us say that you know that your neighbor is dying and with negative effort, cost and risk, you can call an ambulance and save his life. (That is to say that you know that you will be rewarded for doing so after the fact.) It is hard to argue that you are under no moral obligation to help.
So beliefs can compel actions. And if you deny that you may have certain true beliefs P, you can get a situation where you have an action that you are obligated to do (from the fact that P is true and you believe it) but may be barred for moral reasons from doing it because it is immoral.