Cicero's De Divinatione (Latin, "Concerning Divination") is a philosophical treatise in two books written in 44 BC. It takes the form of a dialogue whose interlocutors are Cicero (speaking mostly in Book II) and his brother Quintus.
Cicero concerns himself in some detail with the types of divination, dividing them into the "inspired" type (Latin furor, Gk. mania, "madness"), especially dreams, and the type which occurs via some form of skill of interpretation (i.e., haruspicy, extispicy, augury, astrology, and other oracles).
Book I deals with Quintus' apology of divination (in line with his essentially Stoic beliefs), while Book II contains Marcus' refutation of these from his Academic philosophical standpoint.
It is notable as one of posterity's primary sources on the workings of Roman religion. It also includes a fragment of Cicero's poem on his own consulship.
Nothing so absurd can be said that some philosopher had not said it. (Latin: Sed nescio quo modo nihil tam absurde dici potest quod non dicatur ab aliquo philosophorum) (II, 119)
That old saying by Cato is quite well known; he said he was surprised that one haruspex did not burst out laughing when he saw another one. (Latin: Vetus autem illud Catonis admodum scitum est, qui mirari se aiebat quod non rideret haruspex haruspicem cum vidisset) (II, 24, 51)