I am an atheist. I don't think there's anything divine. Beautiful, impressive, awe-inspiring - sure, but not divine.

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 don't think we are all irrational every time we fail to see through an argument in a book, but suppose it's true about you. You are still more rational than you think you are. You are irrational in a minor way - believing a misguided theory of the nature of rationality - but rational in a major way - you respond well to probabilistic evidence as you go through the day.

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".

I don't think any of my desires or beliefs or other mental states are external to me. Many people will occasionally feel alienated from the motives for an action - "whatever possessed me to do that?". Note, however, that some people feel alienated from the white hairs that recently appeared on their heads - "who put them there?", they might ask the mirror - but the white hairs are still theirs. Similarly, I might feel alienated from an action or a mental state because it does not fit with my visceral self - image.

Suppose whether or not someone tells me a lie depends only on whether he wants to, but he is morally indifferent, he doesn't care much about the truth or about me, and his self interest, which he worships, tells him to lie, and so it comes about that given his psychology, it is a forgone conclusion that he will lie to me. I think in this case he is still blameworthy, and that implies, among other things, that he did something he ought not do.

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".