Lisp
McCarthy designs Lisp, a language built on recursion and symbolic lists, which becomes the native tongue of AI research for thirty years.
what had to happen · 4 events back to 1943
Every event this one built on, transitively, in order. Direct influences are marked.
00 · One neuron · 1
I · Foundations · 3
John McCarthy started designing Lisp at MIT in the autumn of 1958, a year after Fortran, and it is the only language from that era still in daily use. Its premise was that the objects an intelligent program manipulates are not numbers but symbols, and that the natural structure for symbols is the list. Programs themselves were lists, which meant a program could read, build and run other programs, and that a Lisp system could carry an interpreter for itself in a page of code.
The 1960 paper that described it was meant as theory. Steve Russell, one of McCarthy's students, noticed that the eval function on paper could simply be typed in, and did so, producing the first Lisp interpreter almost by accident. Garbage collection, recursion as the basic control structure, functions as values and conditional expressions all arrived with it.
For the symbolic era of AI, Lisp was the environment. Logic Theorist's successors, the expert systems of the 1970s and 80s, ELIZA's descendants and the planners at SRI were written in it, and a whole hardware industry of Lisp machines grew up to run it faster. When that industry collapsed in 1987 it was one of the clearest signals that the second winter had arrived.
what it led to · 7 events downstream, through 1992
Built on it directly:
And, through them, by era: