When certain concepts of TeX are introduced informally, general rules will be stated; afterwards you will find that the rules aren't strictly true. In general, the later chapters contain more reliable information than the earlier ones do. The author feels that this technique of deliberate lying will actually make it easier for you to learn the ideas. Once you understand a simple but false rule, it will not be hard to supplement that rule with its exceptions.

The important thing, once you have enough to eat and a nice house, is what you can do for others, what you can contribute to the enterprise as a whole.

I define UNIX as 30 definitions of regular expressions living under one roof.

The enjoyment of one's tools is an essential ingredient of successful work.

Computers are good at following instructions, but not at reading your mind.

A list is only as strong as its weakest link.

I think people who write programs do have at least a glimmer of extra insight into the nature of God... because creating a program often means that you have to create a small universe