De Natura Deorum (On the Nature of the Gods) is a philosophical dialogue by Roman orator Cicero written in 45 BC. It is laid out in three books, each of which discuss the theology of different Roman and Greek philosophers. The dialogue uses a discussion of Stoic, Epicurean, and skeptical theories to examine fundamental questions of theology.
The dialogue is on the whole narrated by Cicero himself, though he does not play an active part in the discussion. Gaius Velleius represents the Epicurean school, Quintus Lucilius Balbus argues for the Stoics, and Gaius Cotta speaks for Cicero's own Academic skepticism. The first book of the dialogue contains Cicero's introduction, Velleius' case for the Epicurean theology and Cotta's criticism of Epicureanism. Book II focuses on Balbus' explanation and defense of Stoic theology. Book III lays out Cotta's criticism of Balbus' claims. Cicero's conclusions are ambivalent and muted, "a strategy of civilized openness;" he does, however, conclude that Balbus' claims, in his mind, more nearly approximate the truth (3.95).
This work, although not written by an orthodox Epicurean or Stoic, is important because it supplements the scant primary texts that remain from Epicureans or Stoics discussing their views on religion and theology. In particular, heated scholarly debate has focussed on this text's discussion at 1.43-44 of how the Epicurean gods may be said to "exist;" David Sedley, for example, holds that Epicureans, as represented in this text and elsewhere, think that "gods are our own graphic idealization of the life to which we aspire," whereas David Konstan maintains that “the Epicurean gods are real, in the sense that they exist as atomic compounds and possess the properties that pertain to the concept, or prolēpsis, that people have of them."
There is in fact no subject upon which so much difference of opinion exists, not only among the unlearned but also among educated men; and the views entertained are so various and so discrepant, that, while it is no doubt a possible alternative that none of them is true, it is certainly impossible that more than one should be so. (Res enim nulla est, de qua tantopere non solum indocti, sed etiam docti dissentiant; quorum opiniones cum tam variae sint tamque inter se dissidentes, alterum fieri profecto potest, ut earum nulla, alterum certe non potest, ut plus una vera sit) (I, 5)
We, on the contrary, make blessedness of life depend upon an untroubled mind, and exemption from all duties. (We think a happy life consists in tranquility of mind). (Nos autem beatam vitam in animi securitate et in omnium vacatione munerum ponimus) (I, 53)
Because all the sick do not recover, therefore medicine is not an art. (Ne aegri quidem quia non omnes convalescunt, idcirco ars nulla medicina est) (II, 12)
Things perfected by nature are better than those finished by art. (Meliora sunt ea quae natura quam illa quae arte perfecta sunt) (II, 87)
There never was a great man unless through divine inspiration. (Nemo igitur vir magnus sine aliquo adflatu divino umquam fuit) (II, 167)