Meta-design is much more difficult than design; it's easier to draw something than to explain how to draw it.

Email is a wonderful thing for people whose role in life is to be on top of things. But not for me; my role is to be on the bottom of things. What I do takes long hours of studying and uninterruptible concentration.

Beware of bugs in the above code; I have only proved it correct, not tried it.

TeX has found at least one bug in every Pascal compiler it's been run on, I think, and at least two in every C compiler

People who are more than casually interested in computers should have at least some idea of what the underlying hardware is like. Otherwise the programs they write will be pretty weird.

...methods are more important than facts. The educational value of a problem given to a student depends mostly on how often the thought processes that are invoked to solve it will be helpful in later situations. It has little to do with how useful the answer to the problem may be. On the other hand, a good problem must also motivate the students; they should be interested in seeing the answer. Since students differ so greatly, I cannot expect everyone to like the problems that please me.

I can’t go to a restaurant and order food because I keep looking at the fonts on the menu.