Apart from moral conduct, all that man thinks himself able to do in order to become acceptable to God is mere superstition and religious folly. If once a man has come to the idea of a service which is not purely moral, but is supposed to be agreeable to God himself, or capable of propitiating him, there is little difference between the several ways of serving him. For all these ways are of equal value. … Whether the devotee accomplishes his statutory walk to the church, or whether he undertakes a pilgrimage to the sanctuaries of Loretto and Palestine, whether he repeats his prayer-formulas with his lips, or like the Tibetan, uses a prayer-wheel … is quite indifferent. As the illusion of thinking that a man can justify himself before God in any way by acts of worship is religious superstition, so the illusion that he can obtain this justification by the so-called intercourse with God is religious mysticism. Such superstition leads inevitably to sacerdotalism which will always be found where the essence is sought not in principles of morality, but in statutory commandments, rules of faith and observances

Immanuel Kant (1724-1804) German philosopher
Quoted in Karl Hillebrand, Lectures on German Thought, Lecture 5 “The Triumvirate of Goethe, Kant, and Schiller (1787-1800)” (1879)