Donald Knuth on Complexity in Computer Science

In other words, there's still so much more beyond any five pages of my book that you can make a lifetime's worth of study, because there's just that much In computer science. Computer science doesn't all boil down to a bunch of simple things. If it turned out that computer science was very simple, that all you needed to do was find the right 50 things and then learn them really well, then I would say, "OK, everybody in the world should know those 50 things and know them thoroughly."

But It isn't that way. I've got thousands of pages and exercises, and I write it down and put it in the book so that I don't have to have it all in my head. I have to come back to It and learn it again. And I have the answers to the exercises because I know that ten years from now I won't remember I how to do the darn thing and it will take !me a long time to reconstruct it. So I give myself at least the clues to how to reconstruct stuff.

The realm of computer science goes on and on, too expansive for anyone to remember it all.