Most books about natural theology seek to prove or defend God’s existence from nature, reason, etc. They are usually written by adherents of said religion. Every now and then, one will find a text written by an outsider. This might be such a text. It is hard to know exactly what Cicero believed about the gods. My guess is that he believed that belief in them is useful to society, much like how a neoconservative or liberal Protestant believes in “god.”
This book is indispensable for learning the context in which ancient Christianity would later come on scene. It is helpful to remember that the book of Acts was more interested in Epicureans and Stoics than it was in Plato and Aristotle. Moreover, and though Cicero had no interest in this, the text works as a check on erroneous views of God.
We begin with a philosophical retreat to what is ostensibly Cicero’s villa. The gentlemen would know at least three things: do the gods (or God) exist, what are they like, and are they interested in us. The first question is generally granted, even by the skeptic, Cotta. If the gods exist, though, their nature and their existence will be intertwined. For example, it is no good to say that god exists but he is made of parts (or finite, etc.). Such a god would have to be assembled, for example.
Vellius the Epicurean:
He begins by critiquing the weaknesses in earlier natural theology. He makes a number of correct statements, even attacking the idea that the human mind is God (i.e., if it were God, how could it be ignorant of anything?).
Epicurus correctly pointed out that the human mind is a prolepsis, a tool. It is something like a conception and an anticipation. So far, so good. From this he concludes that the gods must exist, for they implanted this conception in our minds.
From here he explains the Epicurean view of “atoms” and that free will is a borderline-irrational swerving of atoms.
Cotta the Academic:
He demolishes all of Vellius’s arguments. Cotta is wrong in his claim that atoms do not exist. We know today that they do. He is correct, however, that atoms do not function the way Vellius says they do. And even if they do function the way Vellius says they do, Cotta delivers the kill shot: if the gods are made of atoms, then they were made that way. They are not eternal. At best, these gods do not have reality, but a mere semblance of reality.
Cotta finishes this section with a number of defeaters, all of them brutal.
Balbus the Stoic:
He has the weakest of all arguments. As weak as his arguments are, Cotta response is not as devastating, for some reason. Balbus’s argument is a design from nature. There must be a designer. I agree, but he needs much more for his theology. He starts strong. He reasons that god or the gods must exist because of divine foreknowledge, blessings, judgments, and the movement of the universe.
Unfortunately, it is not clear that Balbus is talking of God, the gods, or the universe. This makes his argument from design backfire. If there is design in the universe, and the universe is god, then who designed the universe?
Because god is living, and the universe is living, the universe must be god. Not surprisingly, this argument does not convince anyone.
The text at the end is somewhat corrupt, so we will leave it here. The book is valuable for early Christian history as key thinkers like Minicus Felix, Arnobius, and Lactantius (and almost certainly Jerome) read this book.