‘Theme and variations’ is one of those forms that require a certain kind of intellectual activity, because you are always comparing the variation with the theme that you hold in your mind. You might say that the theme is nature and everything that follows is a variation on the subject.

Sometimes, in the middle of a resistant problem, I write down things that I know about it. But you can see the beginning of an idea there, because you can see the word “new” emerging from the “old.” That’s what happens. There’s a relationship between the old and the new; the new emerges from the context of the old. And then I did some variations of it, but it still wasn’t coalescing graphically at all. I had this other version which had something interesting about it in terms of being able to put it together in your mind from clues.

https://www.ted.com/talks/milton_glaser_using_design_to_make_ideas_new