The plain fact is that men's minds are built, as has been often said, in water-tight compartments. Religious after a fashion, they yet have many other things in them beside their religion, and unholy entanglements and associations inevitably obtain. The basenesses so commonly charged to religion's account are thus, almost all of them, not chargeable at all to religion proper, but rather to religion's wicked practical partner, the spirit of corporate dominion. And the bigotries are most of them in their turn chargeable to religion's wicked intellectual partner, the spirit of dogmatic dominion, the passion for laying down the law in the form of an absolutely closed-in theoretic system. The ecclesiastical spirit in general is the sum of these two spirits of dominion; and I beseech you never to confound the phenomena of mere tribal or corporate psychology which it presents with those manifestations of the purely interior life which are the exclusive object of our study. The baiting of Jews, the hunting of Albigenses and Waldenses, the stoning of Quakers and ducking of Methodists, the murdering of Mormons and the massacring of Armenians, express much rather that aboriginal human neophobia, that pugnacity of which we all share the vestiges, and that inborn hatred of the alien and of eccentric and non-conforming men as aliens, than they express the positive piety of the various perpetrators. Piety is the mask, the inner force is tribal instinct. You believe as little as I do, in spite of the Christian unction with which the German emperor addressed his troops upon their way to China, that the conduct which he suggested, and in which other Christian armies went beyond them, had anything whatever to do with the interior religious life of those concerned in the performance.
William James, The Varieties of Religious Experience, Lectures XIV and XV: The Value of Saintliness