Alan Turing
Philosophy Area

thinking by Andrew Hodges
author of Alan Turing: the enigma

See the Alan Turing Home Page for a guide to this website.



Was Alan Turing a philosopher?

Alan Turing would probably have laughed at the idea of being called a great philosopher, or any kind of philosopher. He called himself a mathematician. But his 1950 paper Computing Machinery and Intelligence  has become one of the most cited in modern philosophical literature and people are always arguing about it. This is because he brought the new and rigorous mathematical concept of computability to bear on traditional problems of mind and body, free-will and determinism.

Alan Turing did not think small. Along with the origin of universe, and the origin of life, the question of how 'mind' arises in 'matter' is one of the greatest scientific problems. And it involves the questions about freedom and responsibility that people worry about in every aspect of life.

Am I a philosopher?

No. But Ray Monk, whose biography of Wittgenstein was influenced a bit by Alan Turing: the enigma, invited me to contribute to a series called The Great Philosophers.

The Great Philosopher

My short book Turing: a natural philosopher  appeared in The Great Philosophers  series in 1997, and has now been translated into many languages.

Full details and complete on-line version

There were some thoughts in this book that didn't appear in my earlier biography Alan Turing: the enigma. The main stimulus was the influence of Roger Penrose's books The emperor's new mind and Shadows of the mind. This passage on the influence of the war, for instance, showed the way my thinking had developed since 1983.

Turing in the Land of NZ

Alan Turing's life and work touches on many difficult and controversial subjects so I expect criticism. I was rather surprised, however, by the arguments of two philosophers from New Zealand, Copeland and Proudfoot, who reviewed my work in the Times Literary Supplement.

In April 1999 the philosophers published their extraordinary views on Turing's so-called 'Forgotten ideas' in an article in Scientific American. 

Comment on Copeland and Proudfoot's Oracle

An unexpected result was I found I had more to say about the philosophy of mind and machines than I had realised before.

Here is a lecture, first given at Hamburg in 2000, with the title:

Uncomputability in the work of Alan Turing and Roger Penrose

I was invited by Professor Ed Zalta, the editor of the on-line Stanford Encyclopedia of Philosophy, to submit an entry on Turing's life and thought.

My article 'Alan Turing' in the Stanford Encyclopedia

And in June 2002 I gave a talk which ended the proceedings of the Turing Day at the Federal Institute of Technology, Lausanne, Switzerland.

See my illustrated talk on: What would Alan Turing have done after 1954?

Logical and Physical

In Alan Turing: the enigma I had chosen a formal structure of 'logical' and 'physical' life, with a 'bridge passage' set in 1942-43, and I think this was a good point of departure. When Mike Yates edited the last volume of the Turing Collected Works, he asked me to write a piece on The nature of Turing and the physical world which is also on this site, and I now have a number of other publications which reflect on this theme.

Browse my Publications page.

The ideas can probably be taken yet further. My own attitude is that there is something to learn from every discussion, and I am used to a culture in mathematical physics where people are always having to reshape and adapt their ideas in the light of new insights. Alan Turing himself was basically an applied mathematician, and that's the spirit in which I approach his ideas.

Although I don't agree with Copeland and Proudfoot's conclusions, they have stimulated worthwhile new questions — mainly about how Turing's work relates in fine detail to what is usually called the physical Church-Turing thesis. Also, Copeland noticed one sentence in Turing's 1951 radio talk where he mentioned a problem about quantum mechanics. This is in fact just the objection to Artificial Intelligence theory that Roger Penrose developed into a big new theory in his books. This is all to the good, and I don't mind at all saying that I wish I had noticed this earlier myself!

I am not so keen on philosophers' way of taking up a 'position' and attacking everyone else's, as if it were shameful ever to develop one's views. People argue a great deal about 'Church's thesis' as if it were frozen in time as a dogma. Yes, the historical questions are very interesting, but it might be more interesting to see whether there is a 'Church's synthesis', where logic and physics develop together to give something quite new. This means knowing something about mathematics and physics, not just chopping texts into words.

My detailed review of Copeland's work appears in a special issue of the Notices of the American Mathematical Society. It is available on-line in .pdf form.



Philosophy of Life: Innocence and Experience

In my work I have always wanted to keep in mind Alan Turing as a lively human being, and arid philosophical argument tends to turn him into an textual 'Turing' that I tried to avoid. In addition, his dramatic life and personality continue to raise questions related to moral and political philosophy.

Two publications have more about the moral themes of Alan Turing's extraordinary life as a gay man at the heart of the Anglo-American military machine: Turing — a Cambridge scientific mind and The military use of Alan Turing.

In August 2003 I gave a talk on Alan Turing at Imperial War Museum North. This also formed part of the programme of the lesbian and gay Europride. An article based on my talk, which was designed to link themes of war, sexuality, and science, appears here:




You can also see an illustrated webpage version of my talk on the Turing Collection of screenprints by the distinguished artist and sculptor Sir Eduardo Paolozzi.

Another piece looks at a print by Jin Wicked in a similar way.




Another Road to Reality: mathematics

Roger Penrose has a picture of mind and matter that is not just a relation between logical and physical, but involves three worlds: Platonic, mathematical and physical.

In his more recent The Road to Reality, Roger Penrose leaves aside the question of computability in physics, and gets down to the core of physics itself. Once you are past the first thousand pages you can read about his own vision of what it should be like: twistor theory.

I wrote a little article about The Road to Reality for the Wadham College, Oxford magazine, 2004. See these two pages. Marcus du Sautoy wanted it as a London Mathematical Society review but I said no, this was a human-level piece. Quite appropriately, the article is next to a picture of a cleaning lady holding a toilet roll.



Roger Penrose's Three Worlds.


A lot of my thinking goes into the research in twistor theory that Roger Penrose started.

I'm trying to get a new description of particles and forces by using twistor geometry.

Synthesis of ideas is basic to my way of thinking, and you will find it on my home page and academic page




Continue to: Turing: a natural philosopher (1997)





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Page by Andrew Hodges, updated 26 July 2006

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