I knew him well, obviously, I worked with him, I loved him. I was, I think, close to him. But I never quite understood him, and why should one? Why should one expect to understand one's friends? I mean, he was staggeringly intelligent, I mean, there's no question about that. He... he had this cast of mind, it was not like Medawar's. Medawar's cast of mind ultimately was to reduce it to an experiment and then try and do the experiment. Haldane, confronted with anything from air raid precautions to how genes work, his instinct was to try make... to reduce it to a mathematical model, and the simpler the model the better. And he... he had a real genius for making simple, formal, mathematical models of the world, from which you could deduce what was going to happen. I don't think he was a particularly good mathematician.

[Q] Was he self-taught as a mathematician?

Oh no, no. He'd taken a double first at Oxford in mathematics and classics. He was self-taught as a biologist. He was... he was not a naturalist, I mean his skills were not from natural history, they were essentially from mathematics. And he knew a lot of chemistry, actually, which he'd learnt from his father. He told me once the chemical explanations were much more important than morphological ones, a view that I actually share.