From the last third of the nineteenth century until the middle of the twentieth, official Catholicism, like other sectors of Christianity, had expressed considerable hostility to “Darwinism.” Early Catholic resistance to evolution usually followed from the impression that “Darwinism” is inseparable from “naturalism,” “materialism,” “rationalism, “socialism,” and other creeds taken to be atheistic. From the time of Pope Pius IX (1792–1878) and his promulgation of “The Syllabus of Errors” (1864) until the mid-twentieth century, conservative church officials usually suspected that evolution is especially allied with materialism, the belief that mindless matter is ultimately “all there is” and that therefore God does not exist (Fig. 60.1).

Such a suspicion was not entirely without foundation. During Pius IX’s papacy (1846–78) both Karl Marx and Ernst Haeckel had interpreted Darwin as supporting their own distinct versions of materialism. And in his diaries even Darwin revealed at times his own temptations to materialism. Furthermore, philosophical materialists well into the twenty-first century enthusiastically embraced evolution not only for scientific but also for philosophical reasons. By that time, “postmodern” criticism had called attention to the ideological bias that often accompanies putatively objective discourse, but several highly celebrated biologists and scientific thinkers (e.g., E. O. Wilson, Richard Dawkins, and Daniel Dennett) continued to stitch their evolutionary ideas tightly into a materialist belief system, thus making evolution, at least as they interpreted it, religiously indigestible on any terms. Hence, it is not surprising that scientifically unsophisticated popes and theologians in the late nineteenth and early twentieth century, unable to distinguish clearly between science and materialist beliefs, were often appalled by Darwin’s evolutionary theory.