Edsger Dijkstra

Progress is possible only if we train ourselves to think about programs without thinking of them as pieces of executable code.

Simplicity is prerequisite for reliability.

The purpose of abstraction is not to be vague, but to create a new semantic level in which one can be absolutely precise.

We shall do a much better programming job, provided that we approach the task with a full appreciation of its tremendous difficulty, provided that we stick to modest and elegant programming languages, provided that we respect the intrinsic limitations of the human mind and approach the task as Very Humble Programmers.

The tools we use have a profound and devious influence on our thinking habits, and therefore on our thinking abilities.

LISP has jokingly been described as "the most intelligent way to misuse a computer." I think that description is a great compliment because it transmits the full flavour of liberation: it has assisted a number of our most gifted fellow humans in thinking previously impossible thoughts.

A most important, but also most elusive, aspect of any tool is its influence on the habits of those who train themselves in its use. If the tool is a programming language this influence is, whether we like it or not, an influence on our thinking habits.... A programming language is a tool that has profound influence on our thinking habits.

We must be very careful when we give advice to younger people; sometimes they follow it!

I mentioned the non-competitive spirit explicitly, because these days, excellence is a fashionable concept. But excellence is a competitive notion, and that is not what we are heading for: we are heading for perfection.

Computer science is no more about computers than astronomy is about telescopes.

Aim for brevity while avoiding jargon.

... as a slow-witted human being I have a very small head and I had better learn to live with it and to respect my limitations and give them full credit, rather than to try to ignore them, for the latter vain effort will be punished by failure.

Teaching to unsuspecting youngsters the effective use of formal methods is one of the joys of life because it is so extremely rewarding.

Simplicity and elegance are unpopular because they require hard work and discipline to achieve and education to be appreciated.

We are all shaped by the tools we use, in particular: the formalisms we use shape our thinking habits, for better or for worse, and that means that we have to be very careful in the choice of what we learn and teach, for unlearning is not really possible.

There should be no such thing as boring mathematics.

Program testing can be used to show the presence of bugs, but never to show their absence!

It is practically impossible to teach good programming to students that have had a prior exposure to BASIC: as potential programmers they are mentally mutilated beyond hope of regeneration.

Don't compete with me: firstly, I have more experience, and secondly, I have chosen the weapons.

The students that, like the wild animal being prepared for its tricks in the circus called 'life', expects only training as sketched above, will be severely disappointed: by his standards he will learn next to nothing.

Mathematicians are like managers - they want improvement without change.