About
Alan Turing (1912–1954) was a British mathematician whose work laid the theoretical foundation for computer science and artificial intelligence. His concept of the 'Turing machine' formalized computation itself, while his 1950 paper 'Computing Machinery and Intelligence' introduced the famous 'Turing Test' for machine intelligence. During World War II, he led the team that cracked the Enigma code, helping end the war years earlier. His question 'Can machines think?' launched the field of AI and remains central to debates about artificial minds.
Key Contributions
- Formalized computation with the Turing machine, giving computer science a precise model of what algorithms can do
- Proved limits on computation through work on the Entscheidungsproblem, making undecidability a central idea in computer science
- Asked 'Can machines think?' in 1950 and proposed the imitation game, still the reference point for debates about machine intelligence
- Led key cryptanalytic work at Bletchley Park, including methods and machines used against German Enigma traffic
- Designed the Automatic Computing Engine, one of the early stored-program computer designs after World War II
- Explored morphogenesis with reaction-diffusion equations, showing his interest in computation extended into biology and pattern formation
- His postwar prosecution for homosexuality and later pardon made him a symbol of both scientific brilliance and state persecution
Questions they sharpened View the streams
What is computation?
1936Computation is what a universal machine can do: any procedure that can be written as steps can be mechanized — by one machine that can imitate them all.
Can machines think?
1950Replace the question with a game: if you cannot tell the machine from the person, what exactly is missing?
Videos & Interviews
Papers & Publications
On Computable Numbers, with an Application to the Entscheidungsproblem
1936Defined computability through the universal machine and proved the limits of what any mechanical procedure can decide.
Read PaperComputing Machinery and Intelligence
1950Replaced 'can machines think?' with the imitation game, founding the modern debate on machine intelligence.
Read PaperConnections
Alonzo Church
Influenced byMathematician & Logician
Turing came to Princeton in 1936 to write his doctorate under Church — the one man who had reached the same boundary first, and by a completely different road. Church's lambda calculus defined computation as pure substitution; Turing's machine defined it as a clerk with a tape. That the two turned out to describe exactly the same class of procedures became the Church–Turing thesis, the closest thing computer science has to a law of nature.
plato.stanford.edu · en.wikipedia.org · On Computable Numbers, with an Application to the Entscheidungsproblem (1936)
Ada Lovelace
DebatedMathematician & First Computer Programmer
In 1843 Lovelace wrote that the Analytical Engine 'has no pretensions to originate anything'; in 1950 Turing set that sentence down as objection six of nine and answered it by name. His reading was that the objection really means machines can never take us by surprise — and that they surprised him constantly. It is the strangest argument in this atlas: one party had been dead ninety-eight years, and it is still unsettled.
plato.stanford.edu · doi.org · fourmilab.ch
Ludwig Wittgenstein
DebatedPhilosopher of Language & Logic
In 1939 Turing sat in Wittgenstein's Cambridge lectures on the foundations of mathematics, and the notes students kept record the two of them arguing: Turing defending formalism, Wittgenstein insisting that mathematics does not discover truths but invents them. One man had just defined what it is for a machine to follow a rule; the other was asking what following a rule could even consist in. Every argument about whether a model that follows rules understands them reopens that room.
en.wikipedia.org · en.wikipedia.org · Wittgenstein's Lectures on the Foundations of Mathematics, Cambridge 1939, ed. Cora Diamond (1976)
Kurt Gödel
Influenced byLogician & Mathematician
Turing learned of Gödel's 1931 incompleteness proof from Max Newman's lectures in 1935, and his 1936 answer to Hilbert's decision problem used the same diagonal move to show that no machine can settle every question about what machines will do. Gödel himself was convinced by Turing's analysis that an absolute concept of mechanical computability had been found. Turing's 1938 ordinal logics then asked what a mind is doing when it sees a Gödel sentence to be true that the system cannot prove — the question every argument about machine minds still circles.
plato.stanford.edu · en.wikipedia.org
