“It is simply hard to pinpoint exactly when Darwin had the idea, because the idea didn’t arrive in a flash; it drifted into his consciousness over time, in waves. In the months before the Malthus reading, we could probably say that Darwin had the idea of natural selection in his head, but at the same time was incapable of fully thinking it. This is how slow hunches often mature: by stealth, in small steps. They fade into view.”
