“It is possible and imperative that we discover
A brave and startling truth.”

The Hope of Immortality (Ingersoll Lecture, 1906).

Progress, Coexistence and Intellectual Freedom (1968), Dangers, Police Dictatorships

Journals IV A 87 (1843)
1840s, The Journals of Søren Kierkegaard, 1840s
Context: It seems to be my destiny to discourse on truth, insofar as I discover it, in such a way that all possible authority is simultaneously demolished. Since I am incompetent and extremely undependable in men's eyes, I speak the truth and thereby place them in the contradiction from which they can be extricated only by appropriating the truth themselves. A man's personality is matured only when he appropriates the truth, whether it is spoken by Balaam's ass or a sniggering wag or an apostle or an angel.

Section 56
The True Believer (1951), Part Three: United Action and Self-Sacrifice
Source: The True Believer: Thoughts on the Nature of Mass Movements
Context: It is startling to realize how much unbelief is necessary to make belief possible. What we know as blind faith is sustained by innumerable unbeliefs.
Context: The readiness for self-sacrifice is contingent on an imperviousness to the realities of life.... For self-sacrifice is an unreasonable act.... All active mass movements strive, therefore, to interpose a fact-proof screen between the faithful and the realities of the world.... by claiming that the ultimate and absolute truth is already embodied in their doctrine and that there is no truth nor certitude outside it.... To rely on the evidence of senses and of reason is heresy and treason. It is startling to realize how much unbelief is necessary to make belief possible. What we know as blind faith is sustained by innumerable unbeliefs.

Source: Freedom, Loyalty, Dissent (1954), p. 18

Source: Consilience: The Unity of Knowledge (1998), p. 264.

Source: The Secret Oral Teachings in the Tibetan Buddhist Sects (1964)

As quoted in Angels in the workplace: stories and inspirations for creating a new world of work (1999) by Melissa Giovagnoli
Attributed

Source: Invisible Man (1952), Chapter 7.