I think the basic idea you can easily express in very general terms. Remember, [Alfred Russel] Wallace had the same idea quite independently so it isn’t… it isn’t… so, it's not a very esoteric idea. As… as one has already said, it… it’s an idea which strikes you as obvious, why didn’t you think of it before? Once somebody says it. But to arrive at it is a different matter, you see, and then… as… his case it was because he said he was reading [Thomas Robert] Malthus and this gave him… and he’d been… he got around to the idea that species were not constant and were varying but he didn’t understand what the process would be. And then that gave him the basic idea, and then being a very conscientious man, he worked through, you know, and kept notebooks and collected lots of examples in order to write a treatise on the matter and then he was pushed into it by Wallace essentially so he wrote a short version which is what we call The Origin of Species. That was his idea of a short book. It became a bestseller, incidentally. It was sold out the first day, I think, and had to be reprinted.