In a time such as ours when people believe they can do without an ideal, cast away what they call abstract ideas, live on realism, rationalism, positivism, reduce everything to knowledge or to the use of more or less ingenious and casual devices — let us acknowledge it here — in such a time there is only one means of avoiding error, crime, disaster, of determining the conduct to be followed on a given occasion — but a safe means it is, and a fruitful one; this is the exclusive devotion to two abstract notions in the field of ethics: duty and discipline; such a devotion, if it is to lead to happy results, further implies besides… knowledge and reasoning.

p. 150 - Precepts and Judgments (1919)