Faith as ultimate concern is an act of the total personality. It happens in the center of the personal life and includes all its elements. Faith is the most centered act of the human mind. It is not a movement of a special section or a special function of man's total being. They all are united in the act of faith.
Paul TillichThere is faith in every serious doubt, namely, the faith in the truth as such, even if the only truth we can express is our lack of truth.
Paul TillichWhy does philosophy use concepts and why does faith use symbols if both try to express the same ultimate? The answer, of course, is that the relation to the ultimate is not the same in each case. The philosophical relation is in principle a detached description of the basic structure in which the ultimate manifests itself. The relation of faith is in principle an involved expression of concern about the meaning of the ultimate for the faithful.
Paul Tillich