Science, argues Cicero, makes reliable predictions of events based on the laws of nature. No such reliability is possible for mysticisms like divination.

Cicero says that nobody actually takes soothsayers seriously, because when we want to actually accomplish something, we go to an expert in that domain, like a doctor, and not a to a seer or a prophet.

Cicero is gearing up to respond to his brother's defense of the Stoic notion of divination. He will do so, however, while putting forth probable arguments, not declarations of certainty. As a good critical thinker ought to do.

Cicero explains the main reason he writes philosophy: to be helpful to other people. But we also know he was helping himself to overcome the grief he felt at the death of his beloved daughter Tullia.

Quintus, Cicero's brother, makes one last - and pretty good - argument in favor of divination, an argument that anticipated a famous idea by the astronomer Pierre-Simon de Laplace.

Nothing has happened which was not bound to happen, and, likewise, nothing is going to happen which will not find in nature every efficient cause of its happening.

Quintus, Cicero's brother, mentions Socrates' famous daimon as evidence of divine influence. But it is more likely that Socrates himself simply meant the concept as a way to represent his conscience.

Cicero makes reference to two problems, as we moderns may see them, with Stoic philosophy: the notion of an intelligence permeating the universe, and the idea that the body is a drag on the mind.

Quintus, Cicero's brother, relies on other people's testimony to establish the reality of divination. But as his brother, David Hume, and Carl Sagan observed, that sort of evidence is insufficient to establish his extraordinary claim.

Quintus, Cicero's brother, delivers yet another fallacious argument in defense of divination, one that implies that Epicurus got at least one thing right, despite how much Cicero obviously didn't like him or his philosophy.