One Element of Faith

Out of the element of participation follows the certainty of faith; out of the element of separation follows the doubt in faith. And each is essential for the nature of faith. Sometimes certainty conquers doubt, but it cannot eliminate doubt. The conquered of today may become the conqueror of tomorrow. Sometimes doubt conquers faith, but it still contains faith. Otherwise it would be indifference…
The fundamental symbol of our ultimate concern is God. It is always present in any act of faith, even if the act of faith concerns the denial of God… Atheism, consequently, can only mean the attempt to remove any ultimate concern – to remain unconcerned about the meaning of one’s existence. Indifference toward the ultimate question is the only imaginable form of atheism…
Doubt is not the opposite of faith; it is one element of faith.

Paul Tillich (1886-1965)
Christianity
Dynamics of Faith

Wilson, Andrew, editor. World Scripture II. Universal Peace Federation, 2011, p. 774 [Paul Tillich - Dynamics of faith (1957)].