An ag(e)ing hacker, Luca Saiu's blog
2011-10-25 23:55 (last update: 2014-07-26 14:57) Luca Saiu

I will remember John McCarthy

I’ve just learned that Professor John McCarthy ( died two days ago on October 23, at the age of 84. He was the father of Lisp, Artificial Intelligence, Non-Monotonic Logics and Situation Calculus; and garbage collection, and time-sharing. An amusingly absent-minded brilliant mathematician and thinker with philosophical inclinations, and a technological optimist. I’ve loved reading his lightly sketched deep thoughts in his plain unassuming style1, so different from the pretentious generations of big-egoed Lispers who came after him, myself included. And who even cares now if I agree with what he said one hundred percent, or not; I’ve never met him or communicated with him, but John McCarthy will always be one of my great masters.

Who has been associating with me for some time knows that, and may have seen one of my computers2 named after him. I’m too young to have known Lisp when it was fashionable, but after seeing what other people I admired were writing about it on the Net, I decided to study it. First Common Lisp in the late Nineties, using CLtL2 and in the beginning without understanding much; then, after being exposed to functional programming through other languages, Scheme. Now I’m a convinced Lisper; despite some important differences my epsilon language ( should also be considered at least a Lisp descendant, if not properly a Lisp dialect. And of course Lisp is central for GNU, from a historical and technical point of view. By conscious choice, I am part of that culture. And now John McCarthy is dead.

I was even in a good mood today.

Just this afternoon I’ve taught a class about, among other things, programming in a Lisp dialect. Had I known the news before, I could have spent five minutes telling my students about McCarthy’s contributions. But maybe it’s been better to avoid impassioned speeches. Would they have understood? I don’t want to pollute the memory of such a man with the bored looks of some youngsters who’ve never heard his name before, and would prefer to be somewhere else. And I couldn’t blame them in that case either, as admiration can’t be taught: either you have it or you don’t. Grief can’t be mandatory.

For some time I had considered e-mailing McCarthy to ask him information for a piece I’m still planning to write — you know, vague literary projects and other long-term ideas. Actually I had even told about this idea to a person not too long ago, and I had some problems in explaining her my hesitation. I usually avoid bothering other people, but the problem was not that: my friend understood from the way I spoke that what was keeping me was simply respect. Actually Professor McCarthy was known to be friendly to outsiders contacting him; maybe five years ago I read an enthusiastic report on the web written by a young student — I can’t find a link now — who just sent him an e-mail expressing admiration; McCarthy invited him to his house and the guy went there by bike; the two had a nice relaxed conversation. Even if I’ve been lucky enough to meet in person some of my heroes I understand very well how the student was impressed. Having tea with John McCarthy.

From what I can see in a couple of recent videos McCarthy looked physically tired in his last years, in some discomfort. But his intellect seemed to remain sharp, displaying his usual wit. During a 2009 presentation using a laptop he hit the wrong button by mistake, and then took minutes to painfully click through the graphical interface and move the mouse precisely enough to get back to the point, slowly fighting his hand tremor; and then suddenly, breaking the respectful absolute silence of the audience, he laughed at his own physical difficulties: “Why panic?”. The laugh in response from the audience meant we are with you. The universally unfair condition of being old and frail feels much more wrong in the case of great minds.

Even if I had already prepared the code, and exactly for occasions such as this, I’ve decided that I will not change the color theme of these pages into a somber color, or anything exterior like that. As an iconoclast and a fellow Atheist, I don’t think Professor McCarthy would approve of anything as rhetoric.
My bereavement and the sorrow for the loss of a great master, all of this is real. Web banners or color changes, I leave to the mourners of lesser things.

If you want to celebrate the memory of Professor John McCarthy, read his Recursive Functions of Symbolic Expressions and Their Computation by Machine, Part I. It’s the original paper about Lisp written in 1959: Please go read it now. And think of what a mind we lost.

— Luca Saiu, 2011-10-25 23:55 (last update: 2014-07-26 14:57)

computer-science, english, my-masters, obituaries, parentheses

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My favorite example is A Basis for a Mathematical Theory of Computation, written in 1961-63 when hardly any theory was available to build upon:


Unfortunately that machine has several hardware problems and is now out of service. Anyway I’m happy that other people have had my same idea (, so apparently at least another “mccarthy” computer is currently in use, somewhere. The YeeLoong I’m now running Emacs on is called sussman ( J. Sussman), and I don’t want to rename it. Maybe my next computer.