Purpose has no place in biology, but history has no meaning without it. - George Kubler

The historian's special contribution is the discovery of the manifold shapes of time. The aim of the historian, regardless of his specialty in erudition, is to portray time. He is committed to the detection and description of the shape of time.

I was surprised, while preparing this lecture, to notice how, among my friends who had read the book, a division into two groups appeared. Both groups are equally discerning and educated, and as far as I can tell, equal in numbers. One group is eager to say that they don't understand a word of it, and there are artists and historians among them. Those of the other group claim that they understood it all on first reading, without difficulty. Of course I believe them both, without understanding the combination that separates them so sharply. Perhaps distinctive and contrasting features in the comprehension of works of art are responsible. What I say speaks to some, but not to others. Some are ready, and others are not. But when both someday find that they agree in understanding it, that day may be its last as a book alive in the dissension over its intelligibility.

However useful it is for pedagogical purposes, the biological metaphor of style as a sequence of life-stages was historically misleading, for it bestowed upon the flux of events the shapes and behavior of organisms.