The limits of this volume forbid more than the preceding very brief sketch of the chiefs of the ancient philosophy. For a more detailed account the reader is referred to the Biographical Dictionary edited by Dr. Smith, from which valuable work much of this sketch has been derived. The account of Socrates has been principally derived from Mr. Grote’s admirable history of Greece: in which attention has so successfully been devoted to the history of philosophy and the sophists, that a correct idea of the subject can hardly be acquired without a careful study of that work. It was intended to subjoin a comparison of the systems of the different sects, but it would take more space than can be spared; and it is moreover unnecessary, as, the distinctive tenets of each having been explained, the reader is supplied with sufficient materials to institute such a comparison for himself. He will not wonder that men without the guidance of revelation should at times have lost their way in speculations beyond the reach of human faculties, but will the more admire that genius and virtue which manifested itself in such men as Socrates, Plato, and Cicero, for the perpetual enlightenment of the human race. INTRODUCTION. The following account of the two Books of the Academics is extracted from the Dictionary of Greek and Roman Biography, edited by Dr. W. Smith:— “The history of this work, before it finally quitted the hands of its author, is exceedingly curious and somewhat obscure; but must be clearly understood before we can explain the relative position of those portions of it which have been transmitted to modern times. By comparing carefully a series of letters written to Atticus, in the course of B.C. 45 (Ep. ad Att. xiii. 32;(1) 12, 13, 14, 16, 18, 19, 21, 22, 23, 25, 35, 44), we find that Cicero had drawn up a treatise upon the Academic Philosophy, in the form of a dialogue between Catulus, Lucullus, and Hortensius; and that it was comprised in two books, the first bearing the name of Catulus, the second that of Lucullus. A copy was sent to Atticus; and, soon after it reached him, two new Introductions were composed, the one in praise of Catulus, the other in praise of Lucullus. Scarcely had this been done, when Cicero, from a conviction that Catulus, Lucullus, and Hortensius, although men of highly cultivated minds, and well acquainted with general literature, were known to have been little conversant with the subtle arguments of abstruse philosophy, determined to withdraw them altogether, and accordingly substituted Cato and Brutus in their place. Immediately after this change had been introduced, he received a communication from Atticus, representing that Varro was much offended by being passed over in the discussion of topics in which he was so deeply versed. Thereupon Cicero, catching eagerly at the idea thus suggested, resolved to recast the whole piece, and quickly produced, under the old title, a new and