History of theology

Greek "theologia" (θεολογία) was used with the meaning "discourse on god" around 380 BC by Plato in "The Republic", Book ii, Ch. 18. Aristotle divided theoretical philosophy into "mathematike", "physike" and "theologike", with the last corresponding roughly to metaphysics, which, for Aristotle, included discourse on the nature of the divine.
Drawing on Greek Stoic sources, the Latin writer Varro distinguished three forms of such discourse: mythical (concerning the myths of the Greek gods), rational (philosophical analysis of the gods and of cosmology) and civil (concerning the rites and duties of public religious observance).
Some Latin Christian authors, such as Tertullian and Augustine, followed Varro's threefold usage, though Augustine also used the term more simply to mean 'reasoning or discussion concerning the deity'
In patristic Greek Christian sources, "theologia" could refer narrowly to devout and inspired knowledge of, and teaching about, the essential nature of God.
The Latin author Boethius, writing in the early 6th century, used "theologia" to denote a subdivision of philosophy as a subject of academic study, dealing with the motionless, incorporeal reality (as opposed to "physica", which deals with corporeal, moving realities). Boethius' definition influenced medieval Latin usage.
In scholastic Latin sources, the term came to denote the rational study of the doctrines of the Christian religion, or (more precisely) the academic discipline which investigated the coherence and implications of the language and claims of the Bible and of the theological tradition (the latter often as represented in Peter Lombard's "Sentences", a book of extracts from the Church Fathers).
In the Renaissance, especially with Florentine Platonist apologists of Dante's poetics, the distinction between "poetic theology" ("theologia poetica") and "revealed" or Biblical theology serves as steppingstone for a revival of philosophy as independent of theological authority.
It is in this last sense, theology as an academic discipline involving rational study of Christian teaching, that the term passed into English in the fourteenth century, although it could also be used in the narrower sense found in Boethius and the Greek patristic authors, to mean rational study of the essential nature of God – a discourse now sometimes called theology proper.
From the 17th century onwards, it also became possible to use the term theology to refer to study of religious ideas and teachings that are not specifically Christian (e.g., in the term natural theology which denoted theology based on reasoning from natural facts independent of specifically Christian revelation) or that are specific to another religion.
"Theology" can also now be used in a derived sense to mean "a system of theoretical principles; an (impractical or rigid) ideology".