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.