Perhaps a reference to Marcus Tullius Cicero, De divinatione Book I cc.49-50. The book takes the form of a dialogue between Cicero and his brother Quintus; the arguments which Quintus proposes in favour of divination in the first book are attacked by Marcus in the second. Cicero Volume XX: De Senectute, De Amicitia, De Divinatione, trans W.A. Falconer (Loeb, 1971).