There are several famous arguments for the existence of God. The argument from the First Cause maintains that since in the world every effect has its cause behind it (and every actuality its potentiality), the first effect (and first actuality) in the world must have had its cause (and potentiality), which was in itself both cause and effect (and potentiality and actuality), i.e., God. The cosmological argument maintains that since the world, and all that is in it, seems to have no necessary or absolute (nonrelative) existence, an independent existence (God) must be implied for the world as the explanation of its relations.
The teleological argument maintains that, since from a comprehensive view of nature and the world everything seems to exist according to a certain great plan, a planner (God) must be postulated. The ontological argument maintains that since the human conception of God is the highest conception humanly possible and since the highest conception humanly possible must have existence as one attribute, God must exist. Immanuel Kant believed that he refuted these arguments by showing that existence is no part of the content of an idea. This principle has become very important in contemporary philosophy, particularly in existentialism. The consensus among theologians is that the existence of God must in some way be accepted on faith.