Jeff Shrager writes travel-style close readings of landmark programs — each guide treats one famous piece of historic source code the way a good guidebook treats a city, starting with a map, then touring the major regions, then flagging the details a casual visitor would miss. The repository currently covers three programs: the 1963 Logic Theorist, ELIZA, and SHRDLU, each presented in a standardized format that assumes no familiarity with the original language or hardware and ends with a practical primer for reading the code yourself.
- Shrager openly states the guides were created with AI assistance and cross-checked, but likely contain errors
- A "Ground rules" section requires that behavioral claims be checkable against the quoted source, provenance of each source file be stated up front, and modern analogies be explicitly labeled as analogies rather than implied as lineage
- Contributions are welcomed, with corrections for factual errors and misread code especially encouraged
- Shrager openly states the guides were created with AI assistance and cross-checked, but likely contain errors
- A "Ground rules" section requires that behavioral claims be checkable against the quoted source, provenance of each source file be stated up front, and modern analogies be explicitly labeled as analogies rather than implied as lineage
- Contributions are welcomed, with corrections for factual errors and misread code especially encouraged
Jeff Shrager's repository introduces "executable archaeology" — the practice of recovering, transcribing, and running the original historical source of early computing programs so that the surviving artifact itself, rather than a modern rewrite, can serve as experimental evidence. The main project here is an IPL-V reimplementation of Victor Yngve's 1959–61 MIT sentence generator, run under Herbert A. Simon's account on 25 June 1962, whose surviving printout preserves the program, its phrase-structure grammar, execution traces, and handwritten corrections by Simon and his daughter Katherine.
- The repository also points to separate repos reconstructing the Logic Theorist in two historically distinct forms (LT1 in IPL-I and LT5 in IPL-V) and a full CTSS/IBM 7094 reanimation of Weizenbaum's original ELIZA
- A 2026 arXiv paper by Shrager and a 2025 IEEE Annals paper by Lane et al. provide the formal background
- Six stated principles govern the work, including distinguishing original behavior from behavior introduced by the reconstruction
- The repository also points to separate repos reconstructing the Logic Theorist in two historically distinct forms (LT1 in IPL-I and LT5 in IPL-V) and a full CTSS/IBM 7094 reanimation of Weizenbaum's original ELIZA
- A 2026 arXiv paper by Shrager and a 2025 IEEE Annals paper by Lane et al. provide the formal background
- Six stated principles govern the work, including distinguishing original behavior from behavior introduced by the reconstruction
This repository provides an implementation and recreation of the first published version of the Logic Theory Machine, also known as the Logic Theorist. Originally developed by Allen Newell, J. C. Shaw, and Herbert A. Simon in 1956, this program was designed to prove theorems in propositional logic using principles from Principia Mathematica. The project includes a Python-based interpreter for the IPL-I abstract machine language, tools to run the program against historical axioms and theorems, and utilities to analyze generated proofs.
Main components:
Implementation of the 1956 Logic Theory Machine
Propositional logic based on Principia Mathematica
Python interpreter for the IPL-I language
Tools for running simulations and verifying results
Main components:
Implementation of the 1956 Logic Theory Machine
Propositional logic based on Principia Mathematica
Python interpreter for the IPL-I language
Tools for running simulations and verifying results
This paper details the reconstruction and execution of the Logic Theorist (LT), considered the first artificial intelligence program, originally created in 1955-1956. The authors built a new IPL-V interpreter in Common Lisp and faithfully reanimated LT from code transcribed from a 1963 RAND technical report. The reanimated LT successfully proved 16 of 23 theorems from Principia Mathematica, consistent with the original system's behavior. This work demonstrates "executable archaeology" as a method for understanding early AI systems, highlighting the challenges and insights gained from reconstructing and running historical code.
This GitHub repository contains a re-implementation of the IPL-V programming language and the Logic Theorist (LT) program. It includes the original code transcribed into a TSV format and converted to Lisp, along with documentation and debugging tools.
The Wikipedia article details the Logic Theorist, created in 1956 by Allen Newell, Herbert A. Simon, and Cliff Shaw. Widely considered the first AI program, it successfully proved 38 of the first 52 theorems in Principia Mathematica, even discovering more elegant proofs than those originally crafted by Russell and Whitehead.
Jeff Shrager has reanimated LT in IPL-V with a new implementation.
