The idea of natural religion is one of those arresting ideas which never get fully defined but which nevertheless excite reflection and even controversy whenever they appear. The history of its life within the Christian tradition is a case in point; the idea has been taken as a foundation to be built upon, and it has been rejected as a combination of concepts involving the same sort of contradiction to be found in the notion of a round square. Natural religion has been appealed to as a touchstone of rationality and it has been attacked as illegitimate if not actually blasphemous. An idea capable of producing such reactions cannot be ignored.