Sometimes I think it is my mission to bring faith to the faithless, and doubt to the faithful.
Paul TillichOut 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.
Paul TillichFaith consists in being vitally concerned with that ultimate reality to which I give the symbolical name of God. Whoever reflects earnestly on the meaning of life is on the verge of an act of faith.
Paul Tillich