Natural theology, once also termed physico-theology, is a type of theology that provides arguments for the existence of God based on reason and ordinary experience of nature. This distinguishes it from revealed theology, which is based on scripture and/or religious experiences, and also from transcendental theology, which is based on a priori reasoning.
Marcus Terentius Varro (116 BC – 27 BC) established a distinction between political theology (the social functions of religion), natural theology and mythical theology. His terminology became part of the Stoic tradition and then Christianity through St. Augustine and St. Thomas Aquinas.
Natural theology is thus a type of philosophy, the object of which is explanation of the nature of the gods, or of one supreme God. For monotheistic religions, this principally involves arguments about the attributes or non-attributes of God, and especially the existence of God, using arguments that do not involve recourse to supernatural revelation.
Besides Zarathushtra's Gathas, Plato gives the earliest surviving account of a natural theology. In the Timaeus, written c. 360 BC, we read: "We must first investigate concerning [the whole Cosmos] that primary question which has to be investigated at the outset in every case, — namely, whether it has always existed, having no beginning or generation, or whether it has come into existence, having begun from some beginning." In the Laws, in answer to the question as to what arguments justify faith in the gods, Plato affirms: "One is our dogma about the soul...the other is our dogma concerning the ordering of the motion of the stars".