It is nevertheless quite evident that the deepening, unifying tendency I have been describing is not the only one at work: a continual broadening is going on at the same time. That is, new ideas often do more than just supersede, simplify or unify existing ones. They also extend human understanding into areas that were previously not understood at all – or whose very existence was not guessed at. They may open up new opportunities, new problems, new specializations and even new subjects. And when that happens it may give us, at least temporarily, more to learn in order to understand it all.
