"I have also written a Book on Lying, which though it takes some pains to understand, contains much that is useful for the exercise of the mind, and more that is profitable to morals, in inculcating the love of speaking the truth. This also I was minded to remove from my works, because it seemed to me obscure, and intricate, and altogether troublesome; for which reason I had not sent it abroad. And when I had afterwards written another book, under this title, Against Lying, much more had I determined and ordered that the former should cease to exist; which however was not done. Therefore in this retractation of my works, as I have found this still in being, I have ordered that it should remain; chiefly because therein are to be found some necessary things which in the other are not. Why the other has for its title, Against Lying, but this, Of Lying, the reason is this, that throughout the one is an open assault upon lying, whereas great part of this is taken up with the discussion of the question for and against. Both, however, are directed to the same object. This book begins thus: "Magna quæstio est de Mendacio."