This is the last quote I’ll put up from Walter Kaufmann’s magnificent book Critique of Religion and Philosophy. This one, from pp. 220-221, is on the incompatibility between religion and reason. (I don’t agree with the first sentence of the third paragraph if by it Kaufmann is agreeing to some extent with religion’s claim that we can know things about the universe without using empirical methods.)
In one way, morality will soon go the way of astronomy, physics, and biology: to be sure, it will not become a science; but Christians, too, will soon concede the need for rational discussion of moral questions as well as the relevance of observation—and then Christianity will adopt the position that morality is not of ultimate significance. Today, some Christians may still object: if morality is not of ultimate significance, what is? But it is far from self-evident that rules about permissible and impermissible sexual relations should be more crucial for religion than whether the earth revolves around the sun or whether man is a cousin of the gorilla.
Reason and observation alone will never tell us what to do and how to live; whom, if anybody, we should marry; or how many, if any, children we should want. But it does not follow that religion must answer these questions. Nor does it minimize the crucial distinction between informed and uninformed decisions or between responsible and irresponsible choices.
Christianity has been right in insisting on the limitations of reason and observation; but it has vastly exaggerated them while failing to recognize its own limitations: again and again it has claimed competence in areas where it had none. And from the very beginning it has conceived itself as an enemy of reason and worldly wisdom; it has exerted itself to impede the development of reason, belittled the achievements of reason, and gloated over the setbacks of reason.
In principle, many outstanding Roman Catholic thinkers have maintained that reason and religion need not be enemies but could be complementary. But the peace effected by Roman Catholicism was based on the enslavement of reason, upon its employment in the service of propositions which it was not allowed to question. The vaunted synthesis of reason and faith depended on the stake. When the stake lost its tyrannical effectiveness, the revolve of reason and the long war between reason and faith came to dominate the intellectual history of the West for centuries.
Traditional Christianity has been deeply authoritarian in matters of truth. It has made a supreme virtue of unquestioning docility. Though Luther was initially opposed to authoritarianism, his truculent disparagement of reason drove him back into this tradition; for he soon discoverd that where conscience and conviction are supreme no safeguard remains against fanaticism, stupidity, and immorality. Many a modern Protestant has looked upon the later Luther with embarrassment, thinking: “What a falling off was there!” But it was not caprice that led to Lutheran authoritarianism: the issue on which Luther had staked his Reformation had been unsound. The dichotomy between authoritarianism and the anarchy of the supremacy of conscience is pernicious. But what alternative remains where reason and observation are ruled out of court?