Philo of Larisa, head of the Academy in Athens....inspired Cicero with a passion for philosophy, and in particular for the theories of Skepticism, which asserted that knowledge of the nature of things is in the nature of things unattainable. Such ideas were well judged to appeal to a student of rhetoric who had learned to argue all sides of a case. In his early twenties Cicero wrote the first two volumes of a work on 'inventin'--that is to say, the technique of finding ideas and arguments for a speech; in it he noted that the most important thing was 'that we do not recklessly and presumptuously assume something to be true.' This resolute uncertainty was to be a permanent feature of his thought.