Duties concern things that are voluntary. I do think that if you have a moral duty to bring me back the book you borrowed, that implies, roughly, that your doing so depends on your wanting to do so: if you want to bring me the book, you will. This is not the case if you are stuck at some airport due to a snowstorm, far away from me. This, however, is not the same as "ought" implying a metaphysical "can".

When you find yourself reluctant to sit on a chair because it had unexpectedly collapsed in the past you might shake your head and think "there, I'm so irrational!". But your reluctance to sit on a probably rickety chair is not irrational - you think it's irrational because you have a false view of what irrationality is.

Characters in Hollywood movies encounter a lot of car chases. Characters in novels rarely wash their hands or do their laundry. And in the work of moral psychologists, people deliberate and reflect a lot. They deliberate, one sometimes feels, whenever they perform an action, and certainly whenever they act for good reasons.

Incompatibilists will tell you that a work of art has no meaning unless the artists could have chosen to create a different one, but actual artists often say things like "the book chose me" - that is, the work had to be. Some philosophers would call it "volitional necessity", and a similar case that's discussed is the case of Luther saying "here I stand, I can do no other".

Suppose a student of mine writes in her exam that "morality is completely relative to culture, so nothing is absolutely right or wrong. Because of that, it is absolutely wrong to be culturally intolerant". This student, if she believes what she writes, believes a contradiction. She ought not to believe the contradiction - it's a basic epistemic norm. This is true even if she can't avoid believing it - no amount of studying will show her the light.

I think that if your tenure case depends on your proving what you thought was a mathematical theorem and the proposed theorem turns out to be false just before your tenure decision, and you want to get tenure very badly, there is a sense in which it's perfectly understandable and reasonable of you to wish the proposed theorem were true and provable, even if it's logically impossible for it to be.

People of relatively low intelligence can be morally wonderful if they desire the right and the good (not necessarily under the description "right" or "good"). Their low intelligence sometimes results in their accidentally doing something wrong, but doing something wrong out of low intelligence alone is like stepping on a person's foot because you are (literally) blind or missing a cry for help because you are (literally) deaf. We do not judge the blind or deaf person as morally bad.