In November 1859, on the brink of publication and eagerly anticipating the reaction of the naturalists he most respected, Darwin confided to Alfred Russel Wallace: “If I can convert Huxley I shall be content” (Correspondence, 7: 375). A month later he had apparently succeeded, reporting that Huxley “says he has nailed his colours to the mast, and I would sooner die than give up, so that we are in as fine a frame of mind… as any two religionists” (Correspondence, 7: 432).
The conversion to which Darwin referred was not to an atheistic or materialistic worldview. His goal had been more modest: to corroborate the view that species were mutable and that to explain their appearance it was unnecessary to invoke separate acts of creation. The use of religious language is, however, revealing and was not confined to the metaphor of conversion. Belief in the transmutation of species was described as heretical, as when Darwin thanked Huxley for being “my good and admirable agent for the promulgation of damnable heresies” (Correspondence, 7: 434). After receiving “unmerciful” admonition from his old Cambridge friend Adam Sedgwick, Darwin described himself as a “martyr” (Correspondence, 7: 430). As in religious communities, so in the scientific: Darwin exploited personal testimony.