# Logic Theorist Explained – Everything You Need To Know

Hi there! Let me tell you the fascinating story behind one of the most important early breakthroughs in artificial intelligence – the pioneering Logic Theorist program. This 1956 invention by three scientists opened the door to machines that could prove theorems and reason like humans.

Herbert Simon, the lead inventor, was a true polymath who bridged disciplines. With degrees in political science and economics in addition to a PhD in psychology, he exemplified interdisciplinary thinking. Simon saw the potential for computers to simulate and extend human problem-solving abilities.

His partner, Allen Newell, brought complementary expertise in mathematics, psychology and computer science. Together at RAND Corporation in 1955, they hatched the idea of developing a computer program that could replicate the logical reasoning required to prove complex mathematical theorems. This goal was extremely ambitious given the primitive state of computer technology in the 1950s.

To pull it off, they recruited RAND programmer Cliff Shaw to code the system in IPL, one of the earliest programming languages. After intense work, they achieved a major milestone in computer science and AI history – the first program that could prove logical theorems all on its own.

## The Logic Theorist‘s Impressive Reasoning Abilities

This brilliant system could prove over 70% of the theorems in Chapter 2 of Principia Mathematica, the renowned three-volume work by Alfred North Whitehead and Bertrand Russell. Let me show you how much more elegant the Logic Theorist‘s proofs were:

Theorem Whitehead/Russell‘s Proof Logic Theorist‘s Proof
2.85 22 steps 9 steps
2.81 37 steps 22 steps

The Logic Theorist accomplished this using a method called "heuristic search." First, it took the initial hypothesis as the root node. Then it kept branching out with new deductions based on the rules of logic until it found the goal theorem, like searching through a tree. The program knew how to prune away unnecessary branches to zero in on the most efficient proof. With huge search trees containing millions of possible paths, this pruning was critical.

Simon and his team had achieved a blueprint for human-like symbolic reasoning!

## Presenting an AI Breakthrough Before AI Existed!

Here‘s where the story gets even more interesting. The scientists were building the Logic Theorist in 1955-1956. But the field of "artificial intelligence" didn‘t even exist yet!

That very summer of 1956, computer scientist John McCarthy organized a conference at Dartmouth College where he coined the term AI. Imagine McCarthy‘s surprise when Simon‘s team showed up and demonstrated a working reasoning machine beyond anyone‘s expectations!

This was a landmark event that shaped history. The Logic Theorist immediately provided a tangible target for AI researchers. Its innovative software also drove rapid progress in computer programming. The team developed IPL just to get the system running. IPL went on to inspire Lisp, a language that became a standard for AI.

On the philosophy side, the Logic Theorist fed intense debates about machine intelligence. Could a reasoning system have a "mind" like humans? Its proofs were so sophisticated that philosophers like John Searle argued it supported the concept of strong AI.

## Paving the Way for Modern AI Breakthroughs

The trailblazing Logic Theorist spearheaded so much of what came later in AI. It pioneered fundamental concepts like knowledge representation, heuristic search, and symbolic reasoning that evolved into expert systems and other mainstays of AI research.

While deep neural networks now power many cutting-edge AI applications, the Logic Theorist‘s legacy lives on. Modern techniques like automated theorem proving and graph search algorithms build directly on its foundations. Over six decades later, this brilliant invention still stands as one of the seminal achievements in thinking machines!