Lucullus was thus enabled fully and faithfully to detail the arguments of the chief supporter and reviver in those later ages of the old Platonic Academy. His discourse is chiefly directed against that leading principle of the new Academy, which taught that nothing can be known or ascertained. Recurring to nature, and the constitution of man, he confirms the faith we have in our external senses, and the mental conclusions deduced from them. To this Cicero replies, from the writings of Clitomachus, and of course enlarges on the delusion of the senses—the false appearances we behold in sleep, or while under the influence of phrensy, and the uncertainty of everything so fully demonstrated by the different opinions of the great philosophers, on the most important of all subjects, the Providence of the Gods—the Supreme Good and Evil, and the formation of the world. These two books, the Catulus and Lucullus, of which, as already mentioned, the last alone is extant, were written after the termination of the civil wars, and a copy of them sent by Cicero to Atticus. It occurred, however, to the author soon afterwards, that the characters introduced were not very suitable to the subjects discussed, since Catulus and Lucullus, though both ripe scholars, and well-educated men, could not, as statesmen and generals, be supposed to be acquainted with all the _minutiæ_ of philosophic controversy contained in the books bearing their names. While deliberating if he should not rather put the dialogue into the lips of Cato and Brutus, he received a letter from Atticus, acknowledging the present of his work, but mentioning that their common friend, Varro, was displeased to find that none of his treatises were addressed to him, or inscribed with his name. This intimation, and the incongruity of the former characters with the subject, determined the author to dedicate the work to Varro, and to make him the principal speaker in the dialogue(418). This change, and the reflection, perhaps, on certain defects in the arrangement of the old work, as also the discovery of considerable omissions, particularly with regard to the tenets of Arcesilaus, the founder of the new academy, induced him to remodel the whole, to add in some places, to abridge in others, and to bestow on it more lustre and polish of style. In this new form, the _Academica_ consisted of four books, a division which was better adapted for treating his subject: But of these four, only the first remains. The dialogue it contains is supposed to be held during a visit which Atticus and Cicero paid to Varro, in his villa near Cumæ. His guests entreat him to give an account of the principles of the old Academy, from which Cicero and Atticus had long since withdrawn, but to which Varro had continued steadily attached. This first book probably comprehends the substance of what was contained in the Catulus of the former edition. Varro, in complying with the request