In the third and fourth books, the scene of the dialogue is changed. In order to inspect some books of Aristotelian philosophy, Cicero walks over to the villa of young Lucullus, to whom he had been appointed guardian, by the testament of his illustrious father. Here he finds Cato employed in perusing certain works of Stoical authors; and a discussion arises on that part of the Stoical system, relating to the Supreme Good, which Cato placed in virtue alone. Cicero, in his answer to Cato, attempts to reconcile this tenet with the doctrines of the Academic philosophy, which he himself professed, by showing that the difference between them consisted only in the import affixed to the term _good_—the Academic sect assigning a pre-eminence to virtue, but admitting that external advantages are good also in their decree. Now, the Stoics would not allow them to be good, but merely valuable, eligible, or preferable; so that the sects could be reconciled in sentiments, if the terms were a little changed. The Academical system is fully developed in the fifth book, in a dialogue held within the Academy; and, at the commencement, the associations which that celebrated, though then solitary spot, was calculated to awaken are finely described. “I see before me,” says Piso, “the perfect form of Plato, who was wont to dispute in this very place: These gardens not only recall him to my memory, but present his very person to my senses—I fancy to myself that here stood Speusippus—there Xenocrates—and here, on this bench, sat his disciple Polemo. To me, our ancient Senate-house seems peopled with the like visionary forms; for often when I enter it, the shades of Scipio, of Cato, and of Lælius, and, in particular, of my venerable grandfather, rise up to my imagination.” Here Piso, who was a great Platonist, gives an account, in the presence of Cicero and Cicero’s brother Quintus, of the hypothesis of the old Academy concerning moral good, which was also that adopted by the Peripatetics. According to this system, the _summum bonum_ consists in the highest improvement of all the mental and bodily faculties. The perfection, in short, of everything consistent with nature, enters into the composition of supreme felicity. Virtue, indeed, is the highest of all things, but other advantages must also be valued according to their worth. Even pleasures become ingredients of happiness, if they be such as are included in the _prima naturæ_, or primary advantages of nature. Cicero seems to approve this system, and objects only to one of the positions of Piso, That a wise man must be always happy. Our author thus contrasts with each other the different systems of Greek philosophy, particularly the Epicurean with the Stoical tenets; and hence, besides, refuting them in his own person, he makes the one baffle the other, till he arrives at what is most probable, the utmost length to which the middle or new Academy pretended to reach. The chief part of the work _De