I have collected quotes relevant to my writing for a long time. Here I offer two that are particularly apposite to the craft and ambitions of other non-fiction writers:
The success of the Origin may, I think, be attributed in large part to my having long before written two condensed sketches, and to my having finally abstracted a much larger manuscript, which was itself an abstract. By this means I was enabled to select the more striking facts and conclusions. I had also, during many years, followed a golden rule, namely, that whenever a published fact, a new observation or thought came across me, which was opposed to my general results, to make a memorandum of it without fail and at once; for I had found by experience that such facts and thoughts were far more apt to escape from the memory than favourable ones. Owing to this habit, very few objections were raised against my views which I had not at least noticed and attempted to answer.
Charles Darwin “The Autobiography of Charles Darwin”. Icon Books (2003) p. 60.
Bertrand Russell … dreamt he was on the top floor of the University Library, about A.D. 2100 … A librarian was going around the shelves carrying an enormous bucket, taking down book after book, glancing at them, restoring them to the shelves or dumping them in the bucket. At last he came to three large volumes which Russell could recognize as the last surviving copies of Principia Mathematica. He took down one of the volumes, turned over a few pages, seemed puzzled for a moment by the curious symbolism, closed the volume, balanced it in his hand and hesitated …
G.H, Hardy. Quoted in Paul Hoffman “The Man Who Loved Only Numbers”. Fourth Estate, London (1998), p.111.