He imagined a machine that was only an idea — a head moving over an endless tape — and proved it could compute anything computable at all. That idea is the computer. This book is who he was: mathematician, war-winning codebreaker, and the mind that asked whether machines could think.
A 1936 paper on the limits of computation gave the world the Turing machine.
1912–1954At Bletchley Park he helped break Enigma — work credited with shortening WWII.
BletchleyHis 1950 paper asked "can machines think?" and proposed a test.
the questionProsecuted for being gay in 1952; dead in 1954; pardoned in 2013.
the injusticeAlan Mathison Turing (1912–1954), educated at Cambridge and Princeton, worked at the foundations of logic and computation.
field mathematical logic, then computing
so his deepest work was abstract before it was practical.
+1 he earned his PhD at Princeton in 1938 and could have stayed in the US — he chose to return to Britain.
In 1936 he described an imaginary device — a head reading and writing symbols on an endless tape.
paper "On Computable Numbers" (1936)
so he defined, abstractly, what it means to compute.
+1 he invented it to settle a logic problem — the computer was almost a side effect of the proof.
From 1939 he worked at Bletchley Park, central to breaking Germany's Enigma cipher.
where the Government Code & Cypher School
so his mathematics turned directly into wartime intelligence.
+1 historians estimate the Bletchley effort shortened the war by two to four years.
In 1950 he proposed a test for machine intelligence — now called the Turing Test.
paper "Computing Machinery and Intelligence"
so he opened the field of artificial intelligence.
+1 he answered Ada Lovelace's objection that machines can't originate — a direct reply across a century.
One machine, he showed, could imitate any other — given the right instructions.
idea the universal Turing machine
so a single device could run any program — the core of the computer.
+1 every general-purpose computer you've used is, in theory, a universal Turing machine.
He also proved some problems can never be solved by any machine.
result the halting problem; undecidability
so he drew the boundary of what computation can do.
+1 knowing what's impossible to compute is as foundational as knowing what's possible.
After the war he designed real computers, like the ACE, and worked on early machines at Manchester.
work ACE design; Manchester computing
so he helped build the machines his theory predicted.
+1 he wrote one of the earliest computer chess routines — before hardware could properly run it.
Late in life he turned to how patterns form in nature — the mathematics of biology.
field morphogenesis (1952 paper)
so his last work seeded mathematical biology.
+1 he did this innovative work during his persecution — his mind kept reaching outward regardless.
enihundua series · book no. 0 · a head, a tape, and every computer that followed · the universal machine