Edsger Wybe Dijkstra gave us much more than just technical material and terminology. His deep integrity, wisdom, and compassion came out in so many influential and often fresh and surprising ways --sometimes to the puzzlement of his friends and colleagues. We will have great difficulty in explaining to others what it was like to know Edsger and work with him. Those not fortunate to know him will never understand what they missed.

How do you explain what it was like to take a course on mathematical methodology from Edsger, watching him demonstrate day after day his remarkable ability to solve problems that we can't solve ourselves, even after he elucidates the principles and techniques involved?

You can't.

How do you describe a meeting of his Tuesday Afternoon Club, where participants solved a problem together, or read a paper out loud, sentence by sentence, commenting on sentence structure, style, overall organization, proofs, technical content --on anything that might be improved?

You can't. Tuesday Afternoon Clubs continue, but they will never be the same without their founder, Edsger W. Dijkstra.

How can you explain the experience, which hundreds have had but will have no more, of receiving a handwritten letter from Edsger, filled with interesting technical comments, opinions of people and their work, always with at least one neat play on words, as well as personal information about himself and his family?

You can't. In reading such a letter, one knew that Edsger gave you his undivided attention in a way that few others were willing to do.

How do you demonstrate having a conversation with Edsger, experiencing a minute or two of silence after a question, wondering what is wrong with him, but then to have him come out with a brilliant reply and to realize that he was one of the few people who thought before they spoke?

You can't.

How can you explain the conundrum that to many he seemed aloof and cold, when he was really an amiable, sociable person, who was compassionate and helpful in your time of need and who would drop in on friends in the evening with his wife, unannounced, to chat for an hour?

Impossible to do so. Only those fortunate enough to know Edsger knew the real Edsger.

How do you explain not only his absolute integrity and skill in discriminating between politics and industrial concerns as opposed to scientific goals but also the courage to state these differences in public?

You can't. One less courageous computer scientist once said about a trip report of his, "Edsger is right, but you don't say such things!" Well, Edsger said them because he felt they had to be said.

How is it that Edsger corresponded with so many but coauthored papers with so few? And why was one of them, one of his PhD advisees and closest colleagues, Netty van Gasteren, taken from us in the prime of her life just a month after Edsger passed away? Ah, Netty, we miss you as much as we miss Edsger.

Yes, everyone can read his 1300 essays, trip reports, technical reports, and reviews. But that is not the same as knowing him, talking to him, corresponding with him, socializing with him, and working with him, and we who have had these experiences cannot convey the feeling to others.

Rutger, Marcus, and Femke, you were very wise to choose Ria and Edsger as your parents. While I am sure there were difficulties in growing up in the shadow of such a man, as there are difficulties in any family, you are so much the better for the experience! We hope our paths cross often, for besides liking you for yourself, we see Edsger in you.

Dear Ria, you and Edsger were one. You were with him in his computer science endeavors more than any computer-science wife. You traveled with him and attended lectures, you knew his colleagues as your friends, you welcomed them into your home. Now, you face life with only memories of Edsger. We feel your sorrow and loss. While we can't replace Edsger, we hope that you will continue to befriend us and be part of our lives.

Edsger, you had your physical and mental weaknesses, your human frailties, as we all do. But in many respects, you were a giant among us. The memory of you --your integrity, wisdom, friendship, and compassion-- will inspire us the rest of our lives.