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May 2001 (I wrote this article to help myself understand exactly what McCarthy discovered. You don't need to know this stuff to program in Lisp, but it should be helpful to anyone who wants to understand the essence of Lisp-- both in the sense of its origins and its semantic core. The fact that it has such a core is one of Lisp's distinguishing features, and the reason why, unlike other languages, Lisp has dialects.) In 1960, John McCarthy published a remarkable paper in which he did for programming something like what Euclid did for geometry. He showed how, given a handful of simple operators and a notation for functions, you can build a whole programming language. He called this language Lisp, for "List Processing," because one of his key ideas was to use a simple data structure called a list for both code and data. It's worth understanding what McCarthy discovered, not just as ...

FIFTY YEARS AGO, when I was a boy of fifteen and helping to inhabit a Missourian village on the banks of the Mississippi, I had a friend whose society was very dear to me because I was forbidden by my mother to partake of it. He was a gay and impudent and satirical and delightful young black man -a slave -who daily preached sermons from the top of his master's woodpile, with me for sole audience. He imitated the pulpit style of the several clergymen of the village, and did it well, and with fine passion and energy. To me he was a wonder. I believed he was the greatest orator in the United States and would some day be heard from. But it did not happen; in the distribution of rewards he was overlooked. It is the way, in this world. He interrupted his preaching, now and then, to saw a stick of wood; but the sawing was a pretense -he did it with his mouth; exactly imitating the sound the b...