Having therefore undertaken the office of explaining the truth, I did not think it so necessary to take my commencement from that inquiry which naturally seems the first, whether there is a providence which consults for all things, or all things were either made or are governed by chance; which sentiment was introduced by Democritus, and confirmed by Epicurus. But before them, what did Protagoras effect, who raised doubts respecting the gods; or Diagoras afterwards, who excluded them; and some others, who did not hold the existence of gods, except that there was supposed to be no providence? These, however, were most vigorously opposed by the other philosophers, and especially by the Stoics, who taught that the universe could neither have been made without divine intelligence, nor continue to exist unless it were governed by the highest intelligence. But even Marcus Tullius, although he was a defender of the Academic system, discussed at length and on many occasions respecting the providence which governs affairs, confirming the arguments of the Stoics, and himself adducing many new ones; and this he does both in all the books of his own philosophy, and especially in those which treat of the nature of the gods.