Why did you do it?
Because I chose to do it.
Why did you choose to do it?
Because it was the best available way to get what I wanted.
Why did you want that?
Because it helped bring about what I wanted most overall.
Why did you want that most overall?
Because that's the kind of person I am.
Why are you that kind of person?
Because that's the way I was made by God, nature, and/or society.