Theology is the study of God. From the Greek terms for God (theos) and words (logos), theology literally means “speech about God.” In Christian theology, most major figures speak of theology as a science in the Aristotelian sense of the term, meaning a field of study that starts with given principles and logically builds up a system of knowledge from there.

Anthropology is the study of human beings. From the Greek terms for human being (anthropos) and words (logos), anthropology literally means “speech about human beings.” In the 21st century, anthropology is often associated with sociological and cultural studies of societies in certain places and at particular points in time. Historically, however, anthropology has been simply the study of what it means to be a human.

Taken from the Greek word for “being” (ens; ontos), “ontological” refers to the way in which something exists. In ancient philosophy, the study of being and essence was crucial. Being is the fact that something exists, while essence is the nature of being, or “what the existing thing is like.” Thus, when Feuerbach speaks of ontological proofs, he is speaking about the proof for God from the perspective of being.