The argument of doubt put forward by Locke in favor of tolerance says that we should admit all religions since it is impossible to demonstrate which one is true. This implies that we must not impose beliefs that are not demonstrable. Let us apply this doctrine to ethical principles. It follows that, unless ethical principles can be demonstrated with certainty, we should refrain from imposing them and should tolerate their total denial. But, of course, ethical principles cannot, in a strict sense, be demonstrated: you cannot prove the obligation to tell the truth, to uphold justice and mercy. It would follow therefore that a system of mendacity, lawlessness, and cruelty is to be accepted as the alternative to ethical principles and on equal terms. But a society in which unscrupulous propaganda, violence, and terror prevail offers no scope for tolerance. Here the inconsistency of liberalism based on philosophical doubt becomes apparent: freedom of thought is destroyed by the extension of doubt to the field of traditional ideals, which includes the basis for freedom of thought.(From: —Michael Polanyi, "The Eclipse of Thought," in Meaning, by Michael Polanyi and Harry Prosch [Chicago: University of Chicago Press, 1975], pp. 9-10).