Aristides of Athens wrote in 125 AD. His Apology is the earliest extant Christian apology. It is available online here or in very nice booklet form on Amazon here. Darren Slade (PhD, Theology, Church History) has a very nice summary here of Aristides and his Apology. According to Slade, “His apologetics compelled Hadrian to counter the arbitrary prosecution of Christians (Chron. 2141–42; Hist. eccl. 4.3.3).”

He begins with an argument from beauty and immediately moves into a version of the cosmological argument similar to one of Aquinas’ Five Ways, the argument from motion.

“I, O King, by the grace of God came into this world; and when I had considered the heaven and the earth and the seas, and had surveyed the sun and the rest of creation, I marvelled at the beauty of the world. And I perceived that the world and all that is therein are moved by the power of another; and I understood that he who moves them is God, who is hidden in them, and veiled by them. And it is manifest that that which causes motion is more powerful than that which is moved. But that I should make search concerning this same mover of all, as to what is his nature (for it seems to me, he is indeed unsearchable in his nature), and that I should argue as to the constancy of his government, so as to grasp it fully,–this is a vain effort for me; for it is not possible that a man should fully comprehend it. I say, however, concerning this mover of the world, that he is God of all, who made all things for the sake of mankind . . .”

The Apology is not long and is worth reading in entirety.