The advocatus diaboli, as you know, is not a lawyer employed by the Prince of Darkness. He is a faithful member of the Church whose duty it is, when it is proposed to canonize a saint, to search out all the opposing considerations and to state them as cogently as possible. This wise institution compels the advocates of canonization to exert themselves to develop arguments vigorous enough to overcome all objections. In this symposium on religion, I am asked to serve as advocatus diaboli: to state the Dark Side so that those who follow may have definite positions to attack and may thus more fully develop the strength of their case.
Source: The Faith of a Liberal (NY: Henry Holt, 1946)
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To avoid misunderstanding, I should note at once that my point of view is here not that of the mere logic of ideas and doctrines, but that of the concrete logic of the events of history. From the first point of view, that of the mere logic of ideas and doctrines, it is evident that there are many possible positions other than the “pure” positions which I shall examine. One might ask theoretically and in the abstract, what value these various positions have. That is not what I plan to do. In a word, my point of view is that of the philosophy of culture, and not that of metaphysics.
Source: The Review of Politics 1.1 (Jan 1939): 1-17