From Tillich’s The Courage to Be:

What does self-affirmation mean if there is no self, e.g. in the inorganic realm or in the infinite substance, in being-itself? Is it not an argument against the ontological character of courage that it is impossible to attribute courage to large sections of reality and to the essence of all reality? Is courage not a human quality which can be attributed even to higher animals only by analogy but not properly? Does this not decide for the moral against the ontological understanding of courage? In stating this argument one is reminded of similar arguments against most metaphysical concepts in the history of human thought. Concepts like world soul, microcosmos, instinct, the will to power, and so on have been accused of introducing subjectivity into the objective realm of things. But these accusations are mistaken. They miss the meaning of ontological concepts. It is not the function of these concepts to describe the ontological nature of reality in terms of the subjective or the objective side of our ordinary experience. It is the function of an ontological concept to use some realm of experience to point to characteristics of being-itself which lie above the split between subjectivity and objectivity and which therefore cannot be expressed literally in terms taken from the subjective or the objective side. Ontology speaks analogously. Being as being transcends objectivity as well as subjectivity. But in order to approach it cognitively one must use both. And one can do so because both are rooted in that which transcends them, in being-itself. It is the light of this consideration that the ontological concepts referred to must be interpreted. They must be understood not literally but analogously. This does not mean that they have been produced arbitrarily and can easily be replaced by other concepts. Their choice is a matter of experience and thought, and subject to criteria which determine the adequacy or inadequacy of each of them.