He looked at it, sort of puzzled, and said, ‘Well, do you really need this assumption?’ And I said, well, I suppose we could look at the problem without that assumption. And we went on for a while. And then he said, again, ‘Do you need this other assumption?’…And he kept doing this, about five or six times….At a certain point, I was getting upset, because I saw this neat research problem of mine had become almost trivial. But at a certain point, with all these pieces stripped out, we both saw how to solve it. And then we gradually put all these little assumptions back in and then, suddenly, we saw the solution to the whole problem. And that was just the way he worked.