Plato and Aristotle both posited first cause arguments, though each had certain notable caveats. Plato (c. 427–c. 347 BCE) posited a basic cosmological argument in The Laws (Book X).
He argued that motion in the world and in the cosmos was "imparted motion" that would have required some kind of "self-originated motion" to set it in motion and to maintain the motion. Plato also posited a "Demiurge" of supreme wisdom and intelligence as the creator of the cosmos in his work Timaeus.
For Plato, the demiurge lacked the supernatural ability to create ex nihilo or out of nothing. The demiurge was only able to organize the "anake." The anake was the only other co-existent element or presence in Plato's cosmogony.
Aristotle (c. 384–322 BCE) also put forth the idea of a first cause, often referred to as the "Prime Mover" or "Unmoved Mover" (the πρῶτον κινοῦν ἀκίνητον or primus motor) in his work Metaphysics. For Aristotle too, as for Plato, the underlying "stuff" of the universe always was in existence and always would be (which in turn follows Parmenides' famous statement that "nothing can come from nothing"). Aristotle posited an underlying ousia (an essence or substance) of which the universe is composed, and it is the ousia that the Prime Mover organized and set into motion. The Prime Mover did not organize matter physically, but is instead a Being who constantly thinks about thinking itself, and who organized the cosmos by making matter the object of "aspiration or desire". The Prime Mover was, to Aristotle, a "thinking on thinking," an eternal process of pure thought.