‘Faith‘, for Tillich was the state of being ultimately concerned. Everyone, he said, has an ultimate concern — that which they take for granted without thinking, something they would not surrender for anything.
An ultimate concern could be the nation, a person’s scientific honesty, a political party, a pet, or God. All of these, with the exception of the last one, are finite concerns. ‘Finite‘ means ‘limited‘ or ‘conditioned or “doomed to die’. To raise–something which is finite to an infinite position is to be guilty of idolatry.