Executable Archaeology: Reanimating the Logic Theorist from its IPL-V Source
This work addresses the challenge of preserving and understanding early AI systems for historians and computer scientists, though it is incremental as it focuses on faithful reconstruction rather than new AI advancements.
The researchers tackled the problem of reconstructing and executing the original Logic Theorist AI program from 1955-1956 by building a new IPL-V interpreter in Common Lisp and reanimating it from transcribed code, resulting in the program successfully proving 16 out of 23 theorems from Principia Mathematica, consistent with historical performance.
The Logic Theorist (LT), created by Allen Newell, J. C. Shaw, and Herbert Simon in 1955-1956, is widely regarded as the first artificial intelligence program. While the original conceptual model was described in 1956, it underwent several iterations as the underlying Information Processing Language (IPL) evolved. Here I describe the construction of a new IPL-V interpreter, written in Common Lisp, and the faithful reanimation of the Logic Theorist from code transcribed directly from Stefferud's 1963 RAND technical report. Stefferud's version represents a pedagogical re-coding of the original heuristic logic into the standardized IPL-V. The reanimated LT successfully proves 16 of 23 attempted theorems from Chapter 2 of Principia Mathematica, results that are historically consistent with the original system's behavior within its search limits. To the author's knowledge, this is the first successful execution of the original Logic Theorist code in over half a century.