Evolution is the law of policies: Darwin said it, Socrates endorsed it, Cuvier proved it and established it for all time in his paper on The Survival of the Fittest. These are illustrious names, this is a mighty doctrine: nothing can ever remove it from its firm base, nothing dissolve it, but evolution.

Mark Twain's "Which Was the Dream?" and Other Symbolic Writings of the Later Years (ed. Univ of California Press, 1966) - ISBN: 9780520905054