The human mind is not only, as Calvin has said, a permanent factory of idols, it is also a permanent factory of fears the first in order to escape God, the second in order to escape anxiety; and there is a relation between the two. For facing the God who is really God means facing also the absolute threat of nonbeing. The “naked absolute” (to use a phrase of Luther’s) produces “naked anxiety”; for it is the extinction of every finite self-affirmation, and not a possible object of fear and courage….But ultimately the attempts to transform anxiety into fear are vain. The basic anxiety, the anxiety of a finite being about the threat of nonbeing, cannot be eliminated. It belongs to existence itself.
–Paul Tillich, The Courage to Be (New Haven: Yale University Press, 1st edition 1952, 2nd edition 2000), p.39