Melvyn's newsletter - Logic - 21/10/2010

Illustration for the logic episode.


Immediately after the programme, Professor A C Grayling told us that we had not discussed modal logic, or deontic logic, or epistemic logic, or multi-valent logic. (This, he explained, is to show that there is more than one way of not being true.) Apart from that, we seem to have made a reasonable shot at it - or that was the consensus. One of the contributors said that the hardest thing to explain was Frege, and there was his importance to the philosophy of language, something which had been taken up and explained in great detail by Sir Michael Dummett. I was clearly being given a reading list.

They were all delighted that the problem of abstract mathematics in 1936 had set Turing off on a course which produced a machine which not only led to the computer, but also, according to military experts, shortened the Second World War by about one year. Soon after the war, as you know, he was arrested for an alleged homosexual''offence'' in a public lavatory and later took his own life by injecting an apple with poison.

Peter Millican wondered how we could have got through the programme without mentioning Gödel. He knew that we had previously done a programme on Gödel, but Gödel, it seems, is extremely important here too and we took that rap. One thing that did not come up was the expertise, in fact distinction that Rosanna Keefe has in the area of''vagueness''. Natural language being vague and it is something which she is exploring. A C Grayling, usually more slicingly exact than a Gillette razor, defended vagueness in the following terms: if he rushed into a bedroom at two o'clock in the morning and shouted''Fire!'' this could open a wide range of possibilities for any logical person. Was he talking about a candle being lit downstairs? Was he talking about something that had happened in another place? But we mere mortals would be vague enough to understand that the house was ablaze and rush out. Something to be said for vagueness then.

The limitations of logic were hinted at when one of the contributors said that logic demands that there is one thing or the other, whereas in colours, for example, there are shades of things going all along the spectrum. But maybe I misunderstood this and Frege and Gödel were on to that.

Afterwards, Tom Morris, the Producer, and I went down to the BBC café on the ground floor and filled up the rest of the season until Christmas. We even tipped over into the first programme in January.

Out then into the most wonderful autumn day, when even the air of London appears to be fresh. Certainly on another planet from when I arrived here fifty years ago and ran into a Dickensian London smog. Even the shops looked bright and sparkly. And I'm glad to report that, after a long absence, St James's Park has returned and is still there, full of ducks and full of French children looking at the ducks and feeding the ducks and scaring away the pigeons.

Into the House of Lords for a sad report from the Privileges Committee about the expenses issue, and a disturbing comment from one of our most ardent listeners, who very firmly told me that he could not follow the programme. And if I went into that territory too often, I would lose him and other listeners like him.

And it's only midday.

Best wishes

Melvyn Bragg

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