In De Natura Deorum, On the Nature of the Gods, Cicero stages a debate rather than delivering a lecture. He gives a Stoic, an Epicurean and an Academic Skeptic each a book to argue their position on whether the gods exist, what nature they have, and whether they concern themselves with human affairs, and he closes the dialogue without declaring a winner, letting the reader judge which case is more persuasive. The form itself is an argument: Cicero, trained in the Academic school's method of arguing both sides of a question, treats theology as a subject on which reasoned people can disagree honestly, a stance distinct from both the confident materialism of the Epicureans, who held the gods existed but took no interest in human affairs, and the providential cosmos of the Stoics, who identified the divine with the rational order pervading nature itself.
His companion work, De Divinatione, On Divination, examines augury, oracles and prophetic dreams with the same dialogic method, again dividing the argument between a defender and a skeptic, this time cast as Cicero's own brother Quintus and Cicero himself. The pairing is not incidental: Cicero held the priestly office of augur at Rome for the last years of his life, so the dialogue sets his private philosophical doubt about the reliability of divination against a public religious role he continued to perform, a tension he never fully resolves any more than he resolves the theological debate in the companion work.