Abstract: Cicero's preface to De inventione 1 shows that his early understanding of the interdependence of philosophy and oratory, with particular emphasis on the importance of philosophy, was more advanced than it is usually thought. The thesis or the general question that opens the treatise showcases Cicero's ability to present Greek technical knowledge about rhetoric as a part of a broader—we may say philosophical—problem, foreshadowing the "thetic method" showcased in his later works. Both the preface to De inventione 1 and Cicero's criticism of Hermagoras's views on thesis at De inventione 1.8 reflect the influence of Philo of Larissa, suggesting that the treatise was not finished before 88 BCE.