Dijkstra Quotes & Sayings

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

Yes, I share your concern: how to program well -though a teachable topic- is hardly taught. The situation is similar to that in mathematics, where the explicit curriculum is confined to mathematical results; how to do mathematics is something the student must absorb by osmosis, so to speak. One reason for preferring symbol-manipulating, calculating arguments is that their design is much better teachable than the design of verbal/pictorial arguments. Large-scale introduction of courses on such calculational methodology, however, would encounter unsurmoutable political problems. — Edsger Dijkstra

The art of programming is the art of organizing complexity. — Edsger Dijkstra

[Though computer science is a fairly new discipline, it is predominantly based on the Cartesian world view. As Edsgar W. Dijkstra has pointed out] A scientific discipline emerges with the - usually rather slow! - discovery of which aspects can be meaningfully 'studied in isolation for the sake of their own consistency. — Edsger Dijkstra

Why has elegance found so little following? That is the reality of it. Elegance has the disadvantage, if that's what it is, that hard work is needed to achieve it and a good education to appreciate it. — Edsger Dijkstra

For me it is essential to understand that everyone is alone. Not in the sense of loneliness, but rather in the sense that no one can completely understand someone else. I know very well what Diane Arbus means when she says that one cannot crawl into someone else's skin, but there is always an urge to do so anyway. I want to awaken definite sympathies for the person I have photographed. — Rineke Dijkstra

APL is a mistake, carried through to perfection. It is the language of the future for the programming techniques of the past: it creates a new generation of coding bums. — Edsger Dijkstra

Mentally mutilated potential programmers beyond hope of regeneration. — Edsger Dijkstra

Please don't fall into the trap of believing that I am terribly dogmatical about [the goto statement]. I have the uncomfortable feeling that others are making a religion out of it, as if the conceptual problems of programming could be solved by a single trick, by a simple form of coding discipline! — Edsger Dijkstra

FORTRAN, the infantile disorder, by now nearly 20 years old, is hopelessly inadequate for whatever computer application you have in mind today: it is now too clumsy, too risky, and too expensive to use. — Edsger Dijkstra

My point today is that, if we wish to count lines of code, we should not regard them as "lines produced" but as "lines spent": the current conventional wisdom is so foolish as to book that count on the wrong side of the ledger. — Gotze Dijkstra

Object-oriented programming is an exceptionally bad idea which could only have originated in California. — Edsger Dijkstra

It is not the task of the University to offer what society asks for, but to give what society needs. — Edsger Dijkstra

I don't know how many of you have ever met Dijkstra, but you probably know that arrogance in computer science is measured in nano-Dijkstras. — Alan Kay

Computer science has as much to do with computers as astronomy has to do with telescopes. — Edsger Dijkstra

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. — Edsger Dijkstra

Program testing can be used to show the presence of bugs, but never to show their absence! — Edsger W. Dijkstra

When we take the position that it is not only the programmer's responsibility to produce a correct program but also to demonstrate its correctness in a convincing manner, then the above remarks have a profound influence on the programmer's activity: the object he has to produce must be usefully structured. — Edsger Dijkstra

Simplicity is prerequisite for reliability. — Edsger W. Dijkstra

As a photographer you enlarge or emphasize a certain moment, making it another reality. — Rineke Dijkstra

Simplicity is a great virtue but it requires hard work to achieve it and education to appreciate it. And to make matters worse: complexity sells better. — Edsger W. Dijkstra

Too few people recognize that the high technology so celebrated today is essentially a mathematical technology. — Edsger Dijkstra

Perfecting oneself is as much unlearning as it is learning. — Edsger Dijkstra

The problems of the real world are primarily those you are left with when you refuse to apply their effective solutions. — Edsger Dijkstra

Our intellectual powers are rather geared to master static relations and that our powers to visualize processes evolving in time are relatively poorly developed. For that reason we should do (as wise programmers aware of our limitations) our utmost to shorten the conceptual gap between the static program and the dynamic process, to make the correspondence between the program (spread out in text space) and the process (spread out in time) as trivial as possible. — Edsger Dijkstra

In their capacity as a tool, computers will be but a ripple on the surface of our culture. In their capacity as intellectual challenge, they are without precedent in the cultural history of mankind. — Edsger Dijkstra

In this respect a program is like a poem: you cannot write a poem without writing it. Yet people talk about programming as if it were a production process and measure "programmer productivity" in terms of "number of lines of code produced". In so doing they book that number on the wrong side of the ledger: we should always refer to "the number of lines of code spent". — Edsger Dijkstra

If in physics there's something you don't understand, you can always hide behind the uncharted depths of nature. You can always blame God. You didn't make it so complex yourself. But if your program doesn't work, there is no one to hide behind. You cannot hide behind an obstinate nature. If it doesn't work, you've messed up. — Edsger Dijkstra

The lurking suspicion that something could be simplified is the world's richest source of rewarding challenges. — Edsger Dijkstra

I don't need to know anything about the people I photograph, but it's important that I recognize something about myself in them. — Rineke Dijkstra

It is not only the violin that shapes the violinist, we are all shaped by the tools we train ourselves to use, and in this respect programming languages have a devious influence: they shape our thinking habits. — Edsger W. Dijkstra

In the wake of the Cultural Revolution and now of the recession I observe a mounting pressure to co-operate and to promote "teamwork". For its anti-individualistic streak, such a drive is of course highly suspect; some people may not be so sensitive to it, but having seen the Hitlerjugend in action suffices for the rest of your life to be very wary of "team spirit". Very. — Edsger Dijkstra

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

Your obligation is that of active participation. You should not act as knowledge-absorbing sponges, but as whetstones on which we can all sharpen our wits — Edsger W. Dijkstra

About the use of language: it is impossible to sharpen a pencil with a blunt axe. It is equally vain to try to do it with ten blunt axes instead. — Edsger Dijkstra

The traditional mathematician recognizes and appreciates mathematical elegance when he sees it. I propose to go one step further, and to consider elegance an essential ingredient of mathematics: if it is clumsy, it is not mathematics. — Edsger Dijkstra

If we wish to count lines of code, we should not regard them as 'lines produced' but as 'lines spent.' — Edsger Dijkstra

Some consider the puzzles that are created by their omissions as spicy challenges, without which their texts would be boring; others shun clarity lest their work is considered trivial. — Edsger Dijkstra

It used to be the program's purpose to instruct our computers; it became the computer's purpose to execute our programs. — Edsger Dijkstra

Lisp has jokingly been called "the most intelligent way to misuse a computer". I think that description is a great compliment because it transmits the full flavor of liberation: it has assisted a number of our most gifted fellow humans in thinking previously impossible thoughts. — Edsger Dijkstra

When we had no computers, we had no programming problem either. When we had a few computers, we had a mild programming problem. Confronted with machines a million times as powerful, we are faced with a gigantic programming problem. — Edsger Dijkstra

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. — Edsger Dijkstra

Elegance is not a dispensable luxury but a factor that decides between success and failure. — Edsger Dijkstra

The use of COBOL cripples the mind; its teaching should, therefore, be regarded as a criminal offense. — Edsger W. Dijkstra

Programming is one of the most difficult branches of applied mathematics; the poorer mathematicians had better remain pure mathematicians. — Edsger Dijkstra

... what society overwhelmingly asks for is snake oil. Of course, the snake oil has the most impressive names - otherwise you would be selling nothing - like "Structured Analysis and Design", "Software Engineering", "Maturity Models", "Management Information Systems", "Integrated Project Support Environments" "Object Orientation" and "Business Process Re-engineering". — Edsger Dijkstra

A convincing demonstration of correctness being impossible as long as the mechanism is regarded as a black box, our only hope lies in not regarding the mechanism as a black box. — Edsger Dijkstra

Brainpower is by far our scarcest resource. — Edsger Dijkstra

With young people everything is much more on the surface - all the emotions; when you get older you know how to hide things. — Rineke Dijkstra

In the good old days physicists repeated each other's experiments, just to be sure. Today they stick to FORTRAN, so that they can share each other's programs, bugs included. — Edsger Dijkstra

Computer Science is no more about computers than astronomy is about telescopes — Edsger W. Dijkstra

I would therefore like to posit that computing's central challenge, how not to make a mess of it, has not yet been met. — Edsger Dijkstra

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

John von Neumann draws attention to what seemed to him a contrast. He remarked that for simple mechanisms, it is often easier to describe how they work than what they do, while for more complicated mechanisms, it is usually the other way around. — Edsger Dijkstra

By claiming that they can contribute to software engineering, the soft scientists make themselves even more ridiculous. (Not less dangerous, alas!) In spite of its name, software engineering requires (cruelly) hard science for its support. — Edsger W. Dijkstra

The prisoner falls in love with his chains. — Edsger Dijkstra

Aim for brevity while avoiding jargon. — Edsger Dijkstra

There is very little point in trying to urge the world to mend its ways as long as that world is still convinced that its ways are perfectly adequate. — Edsger Dijkstra

I felt that the beach portraits were all self-portraits. That moment of unease, that attempt to find a pose, it was all about me. — Rineke Dijkstra

A photo is always a kind of lie. Truth is only present for a matter of a fraction of a second. — Rineke Dijkstra

Mathematicians are like managers - they want improvement without change. — Edsger Dijkstra

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

Don't blame me for the fact that competent programming, as I view it as an intellectual possibility, will be too difficult for the average programmer, you must not fall into the trap of rejecting a surgical technique because it is beyond the capabilities of the barber in his shop around the corner. — Edsger Dijkstra

The competent programmer is fully aware of the limited size of his own skull. He therefore approaches his task with full humility, and avoids clever tricks like the plague. — Edsger Dijkstra

Probably I am very naive, but I also think I prefer to remain so, at least for the time being and perhaps for the rest of my life. — Edsger Dijkstra

The effective exploitation of his powers of abstraction must be regarded as one of the most vital activities of a competent programmer. — Edsger Dijkstra

If debugging is the process of removing software bugs, then programming must be the process of putting them in. — Edsger Dijkstra

Beware of "the real world". A speaker's apeal to it is always an invitation not to challenge his tacit assumptions. — Edsger Dijkstra

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. — Edsger Dijkstra

So-called "natural language" is wonderful for the purposes it was created for, such as to be rude in, to tell jokes in, to cheat or to make love in (and Theorists of Literary Criticism can even be content-free in it), but it is hopelessly inadequate when we have to deal unambiguously with situations of great intricacy, situations which unavoidably arise in such activities as legislation, arbitration, mathematics or programming. — Edsger Dijkstra

The question of whether a computer can think is no more interesting than the question of whether a submarine can swim. — Edsger W. Dijkstra

Industry suffers from the managerial dogma that for the sake of stability and continuity, the company should be independent of the competence of individual employees. — Edsger Dijkstra

I think of the company advertising "Thought Processors" or the college pretending that learning BASIC suffices or at least helps, whereas the teaching of BASIC should be rated as a criminal offence: it mutilates the mind beyond recovery. — Edsger Dijkstra

In the software business there are many enterprises for which it is not clear that science can help them; that science should try is not clear either. — Edsger Dijkstra

Teaching COBOL ought to be regarded as a criminal act. — Edsger Dijkstra

If there is one 'scientific' discovery I am proud of, it is the discovery of the habit of writing without publication in mind. — Edsger Dijkstra

I mean, if 10 years from now, when you are doing something quick and dirty, you suddenly visualize that I am looking over your shoulders and say to yourself "Dijkstra would not have liked this", well, that would be enough immortality for me. — Edsger W. Dijkstra

When I came back from Munich, it was September, and I was Professor of Mathematics at the Eindhoven University of Technology. Later I learned that I had been the Department's third choice, after two numerical analysts had turned the invitation down; the decision to invite me had not been an easy one, on the one hand because I had not really studied mathematics, and on the other hand because of my sandals, my beard and my "arrogance" (whatever that may be). — Edsger Dijkstra

Simplicity and elegance are unpopular because thy require hard work and discipline to achieve and education to be appreciated. — Edsger W. Dijkstra

The effort of using machines to mimic the human mind has always struck me as rather silly. I would rather use them to mimic something better. — Edsger Dijkstra

In passing I draw attention to another English expression which often occurs in Dutch texts: "the real world". In Dutch - and I am afraid not in Dutch alone - its usage is almost always a symptom of a violent anti-intellectualism. — Edsger Dijkstra

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. — Edsger Dijkstra

Several people have told me that my inability to suffer fools gladly is one of my main weaknesses. — Edsger Dijkstra

A programming language is a tool that has profound influence on our thinking habits. — Edsger Dijkstra

I do think that my work has gotten calmer, and that the violence of some of the earlier series was necessary to reach the higher degree of concentration in the later ones. — Rineke Dijkstra

It is a mistake to think that programmers wares are programs. Programmers have to produce trustworthy solutions and present it in the form of cogent arguments. Programs source code is just the accompanying material to which these arguments are to be applied to. — Edsger Dijkstra

When building sand castles on the beach, we can ignore the waves but should watch the tide. — Edsger Dijkstra

Thanks to the greatly improved possibility of communication, we overrate its importance. Even stronger, we underrate the importance of isolation. — Edsger Dijkstra

The use of anthropomorphic terminology forces you linguistically to adopt an operational view. And it makes it practically impossible to argue about programs independently of their being executed. — Edsger Dijkstra

Many mathematicians derive part of their self-esteem by feeling themselves the proud heirs of a long tradition of rational thinking; I am afraid they idealize their cultural ancestors. — Edsger Dijkstra

There should be no such thing as boring mathematics. — Edsger Dijkstra

I don't need to waste my time with a computer just because I am a computer scientist. — Edsger Dijkstra

If you want more effective programmers, you will discover that they should not waste their time debugging, they should not introduce the bugs to start with. — Edsger Dijkstra

Are you quite sure that all those bells and whistles, all those wonderful facilities of your so called powerful programming languages, belong to the solution set rather than the problem set? — Edsger Dijkstra

The computing scientist's main challenge is not to get confused by the complexities of his own making. — Edsger Dijkstra

The ability of discerning high quality unavoidably implies the ability of identifying shortcomings. — Edsger Dijkstra

I am interested in the paradox between identity and uniformity, in the power and vulnerability of each individual and each group. It is in this paradox that I try to visualize by concentrating on poses, attitudes, gestures, and gazes. — Rineke Dijkstra

Experience does by no means automatically leads to wisdom and understanding. — Edsger Dijkstra

For me, the importance of photography is that you can point to something, that you can let other people see things. Ultimately, it is a matter of the specialness of the ordinary. — Rineke Dijkstra

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. — Edsger Dijkstra