trust too much to the impressions of the senses. Cicero even ranks Plato himself with those philosophers who held that there was no such thing as certainty in any kind of knowledge. Later philosophers, either by insisting exclusively on the uncertainty of the senses, like Arcesilaus, or like Carneades and Philo, by extending the same to reason, had fallen into a degree of scepticism that seemed to strike at the root of all truth, theoretical and practical. It was, therefore, the chief object of Antiochus, besides promoting particular doctrines in moral philosophy, to examine the grounds of our knowledge, and our capacities for discovering truth; though no complete judgment can be formed of his success, as the book in which Cicero gave the fullest representation of his opinions has been lost. Antiochus professed to be reviving the doctrines of the Old Academy, or of Plato's school, when he maintained, in opposition to Philo and Carneades, that the intellect had in itself a test by which it could distinguish truth from falsehood; or in the language of the Academics, discern between the images arising from actual objects and those conceptions that had no corresponding reality. For the argument of the sceptics was, that if two notions were so exactly similar as that they could not be distinguished, neither of them could be said to be known with more certainty than the other; and that every true notion was liable to have a false one of this kind attached to it: therefore nothing could be certainly known. This reasoning was opposed by the assertion that the mind contained within itself the standard of truth and falsehood; it was also attacked more generally by the argument that all such reasoning refutes itself, since it proceeds upon principles assumed to be true, and then concludes that there can be no certain ground for any assumption at all. In this manner Antiochus seems to have taken the side of the Stoics in defending the senses from the charge of complete uncertainty brought against them by the Academics. It is evident that in such discussions the same questions were examined which had formerly been more thoroughly sifted by Plato and Aristotle, in analyzing the nature of science and treating of the different kinds of truth, according as they were objects of pure intellectual apprehension, or only of probable and uncertain knowledge. The result was an attempt