Plato was talking about theology centuries before Christianity existed
Theology sounds like a church invention, but Plato used the Greek word for discourse on God around 380 BC. He even argued against atheism, claiming divine souls steer the stars. Aristotle made theology a branch of philosophy, and a Roman scholar split it into mythical, rational and civic kinds.
Theology studies religious belief from inside a religious viewpoint, asking about the nature of the divine and about revelation: whether gods not only stand above nature but act within it and make themselves known. It is taught at universities and seminaries. Theologians use philosophical, historical, experiential and ethnographic arguments, often reasoning by analogy from questions already settled, much as case law does. The work can deepen faith, reform a tradition, compare religions, or challenge them outright, as biblical criticism does.
The word joins Greek theos, god, with logia, sayings or oracles, a relative of logos, reason or account. It travelled through Latin theologia and French théologie, and English settled on its modern spelling by 1362. Its English meaning grew out of early and medieval Christian usage, though the term now reaches far beyond Christianity.
The Greek roots run deep. In The Republic, Plato used theologia around 380 BC, and in Book 10 of the Laws he built a rational theology, holding that the gods' intelligence moves the heavenly bodies and that these gods care for people and for the good of the whole cosmos. Aristotle sorted theoretical knowledge into mathematics, physics and theology, the last roughly what we call metaphysics.
Rome added structure. Drawing on Stoic sources, Varro distinguished mythical theology about the stories of the gods, rational theology about gods and cosmos, and civil theology about public rites and duties. Tertullian and Augustine adopted this scheme, though Augustine also defined theology simply as reasoning about the Deity. In the early 6th century Boethius treated it as the part of philosophy concerned with motionless, bodiless reality, in contrast with physics, and that definition shaped medieval Latin learning.
Source: Theology
