The hallmark of the Enlightenment was “free thought,” that is, the pursuit of knowledge by means of unfettered human reason alone. While it’s by no means inevitable that such a pursuit must lead to non-Christian conclusions and while most of the original Enlightenment thinkers were themselves theists, it has been the overwhelming impact of the Enlightenment mentality that Western intellectuals do not consider theological knowledge to be possible. Theology is not a source of genuine knowledge and therefore is not a science (in German, a Wissenschaft). Reason and religion are thus at odds with each other. The deliverances of the physical sciences alone are taken as authoritative guides to our understanding of the world, and the confident assumption is that the picture of the world which emerges from the genuine sciences is a thoroughly naturalistic picture.