Sir

The retrospective review, by David Jones, of The Scientist Speculates says “how they kept J. B. S. Haldane out of it [the book] remains a mystery” (Nature 393, 642; 1998). I am writing to resolve that mystery.

A nice article by Haldane was accepted, but he was annoyed when the publishers put out an advance leaflet in which Arthur Koestler was put at the head of a list of scientific contributors. Haldane regarded that as inappropriate and withdrew his article. It was published later in Science News (Penguin).

On another point, my guess in 1962 for the cost of reaching full artificial intelligence by 1978 was $108.7 ± 1, so the 95% interval was from $5 million to $50 billion. This guess was not refuted!