The area of verbal humour in Celestina is a complex one, including as it does the use of sententiae and old saws, dirty jokes and puns, sarcasm and academic jests, and what has been designated the rise and fall of speech levels, from lofty rhetoric to a more realistic type of speech. Although the latter is not intrinsically comic, it is often used for humorous effect. The ironic use of sententiae and proverbs is a field which has been covered by a number of inquiries into Celestina. Rojas uses both the aphorisms of the ancients (sententiae, dichos) and the folk proverbs or old saws (refranes) of fifteenth-century Spain ironically, thereby undermining the authority of the speakers who deploy them and the authority of the sayings themselves. As these sayings were the grout which held together the social fabric of medieval Spanish society, the sabotage of this basic material leads to an inversion and collapse of values. Celestina is the chief perpetrator of this attack on received wisdom; she habitually uses aphorisms and old saws to give good advice which will lead to the downfall of her innocent prey Pármeno and Melibea. Rojas exposes the emptiness and treachery of rhetoric and received wisdom in the subversive use of these aphorisms culled from his law books.