**Alan Turing? Arthur Eddington? Andrew Hodges? Robin Gandy? John D. Barrow? Dermot Turing? Apocryphal?**

**Question for Quote Investigator:** Apparently, the pioneering computer scientist Alan Turing once compared scientific knowledge to a differential equation and suggested that religion specified a boundary condition for the equation. I have not seen a precise citation. Would you please explore this topic?

**Reply from Quote Investigator:** In 1983 British mathematician Andrew Hodges published a biography titled “Alan Turing: The Enigma”. Hodges stated that in March 1954 Alan Turing sent four postcards to his friend and colleague Robin Gandy. The second postcard (partially shown below) contained the following lines. Boldface added to excerpts by **QI**:^{[1]}1984 (1983 Copyright), Alan Turing: The Enigma by Andrew Hodges, Chapter 8: On the Beach, Time Period: To 7 June 1954, Quote Page 512 to 514, A Touchstone Book: Simon & Schuster, New York. … Continue reading

Messages from the Unseen World

III. The Universe is the interior of the Light Cone of the Creation

IV.

Science is a Differential Equation. Religion is a Boundary Condition.Arthur Stanley

The postcard also contained the following line written sideways in the left margin:

? Does the gravitation constant decrease ?

Turing’s message presented a playful interpretation of contemporary cosmological theories. The line “Arthur Stanley” referred to English astronomer Arthur Stanley Eddington, and the beginning line perhaps alluded to Eddington’s 1929 book “Science and the Unseen World”. Gandy stated that he and Turing had been discussing Eddington’s book titled “Fundamental Theory”.^{[2]}Website: The Turing Digital Archive, Images scanned from the collection of Turing papers held in the Archive Centre at King’s College, Cambridge, Website description: Website contains nearly … Continue reading

**QI** conjectures that Turing’s statement was an analogy. A differential equation may have many possible solutions. A boundary condition is an extra constraint that reduces the number of possible solutions and sometimes specifies a unique solution. The postcard statement suggested that there were many possible universes that were compatible with the latest scientific knowledge. Religious beliefs provided additional assumptions that further constrained the set of possible universes.

Additional detailed information is available in the Quote Investigator article on the Medium website which is available here.

Image Notes: A public domain mathematical figure from the 1877 book “A Treatise on Some New Geometrical Methods” by James Booth.

References

↑1 | 1984 (1983 Copyright), Alan Turing: The Enigma by Andrew Hodges, Chapter 8: On the Beach, Time Period: To 7 June 1954, Quote Page 512 to 514, A Touchstone Book: Simon & Schuster, New York. (Verified with scans) |
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↑2 | Website: The Turing Digital Archive, Images scanned from the collection of Turing papers held in the Archive Centre at King’s College, Cambridge, Website description: Website contains nearly 3,000 images of letters, photographs, newspaper articles, and unpublished papers by or about Alan Turing. (Accessed turingarchive.kings.cam.ac.uk on January 5, 2023) link |