McCulloch and Pitts model the neuron as a logic gate
A psychiatrist and a homeless teenage logician sketch the first artificial neural network on paper
Quick facts
- Authors
- Warren McCulloch, Walter Pitts
- Published in
- Bulletin of Mathematical Biophysics, Vol. 5
- Institution
- University of Illinois College of Medicine / University of Chicago
What happened
Warren McCulloch, a neurophysiologist at the University of Illinois, and Walter Pitts, a largely self-taught logician, published 'A Logical Calculus of the Ideas Immanent in Nervous Activity' in the Bulletin of Mathematical Biophysics. They argued that because a neuron either fires or does not, its all-or-none behavior can be treated with propositional logic. They showed that a network of these simplified neurons, wired together with weighted connections, could compute any expression that logic itself could express, and that for any such logical statement a net could be built to match its behavior. There was no learning rule and no hardware; it was a mathematical proof that logic and neural wiring could be made equivalent.
Why it matters
The paper gave later researchers, including John von Neumann, a formal bridge between brains and computing machines, and it is the ancestor of every artificial neural network built since, from the perceptron to today's deep networks.
How we know
The original paper is archived and readable in full; it lays out the neuron model and proofs directly, with no learning or training involved, only fixed logical wiring.
Sources
- Warren S. McCulloch and Walter Pitts, Bulletin of Mathematical Biophysics. A Logical Calculus of the Ideas Immanent in Nervous Activity · Primary source (author-declared)home.csulb.edu · Cited as a "primary" source (no stronger domain match).
- Machine Learning @ UChicago. History, Birthplace of Neural Networks: McCulloch and Pitts · Reputable sourcemachinelearning.uchicago.edu · The domain "machinelearning.uchicago.edu" is on our Reputable source registry. · Link is live and its text matches the event's key terms (Jul 2026)
See something wrong? . Corrections with a source get fixed fastest.
Part of a timelineArtificial Intelligence30 events · From a wartime theory of neurons to machines that write, paint, and fold proteinsView all →