When I see two owls and then two more owls and conclude that I see four owls, I am responding to reasons, and it better not be my choice to believe that two plus two always equals four. If I am a rational person, I will have that belief by necessity, whether I wanted to or not. So it's not that strange to discuss responding to reasons out of necessity.

If I am told my loving you had to happen because of some Freudian stuff about my childhood, that might be degrading or deflationary, but if I am told it had to happen because you are such a wonderful person that I couldn't possibly resist your charms, or because we are so incredibly compatible, then necessity seems very romantic.

If I make a stupid decision but don't execute it because I'm, say, lazy, then I'm lucky, not rational. However, at other times a person acts for good reasons just as she does what she thinks she shouldn't do, not knowing that they are good reasons. Just like sometimes we are a lot less rational than we think we are, it is also true that sometimes we are a lot more rational than we think we are.

For those of us who want to have control over all our mental states, compatibilist substitutes - such as desiring what we desire to desire - will always be like being told, when you desperately want there to be a God, that yes, God exists, as God is simply the good within people.

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.

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".

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.