[RKV]

Good question - see also

Honorable Mention

Origin of the Species
by Charles Darwin
Score: 17

Introduction to Psychoanalysis
by Sigmund Freud
Score: 9

Descent of Man
by Charles Darwin
Score: 2

[newheart]

Personally I would place Origin of the Species at number 1. Certainly neither Marx, nor Hitler's books would have had the philosophical underpinnings they did except for Darwin's efforts.

Although the story has not been proved to be true, I have even heard something to the effect that Marx wanted to dedicate Das Kapital to Darwin but Darwin declined. Even if apocryphal, it would fit. We do know that Marx greatly admired Darwin and without question the notion of dialectical materialism could only arise in a milieu which readily accepted the logical consequences of Darwinian naturalism.

And by the way, lest we forget, the full title is: "On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life."

[inquest]

Those other ones aren't all that surprising from a conservative standpoint. But I always thought of J.S. Mill as being one of the primary spokesmen for classical liberalism (=modern economic and political conservatism).