When we study the history of philosophy today, we not only read the original works of philosophers, but we also make extensive use of handbooks and reference works. It was no different in the time of Philo. The Alexandrian’s vast knowledge of Greek philosophy was certainly based on extensive reading of original texts. But there is also clear evidence that he made use of various kinds of handbook literature. One example that we can trace is his use of the Placita literature, which is still extant under the name of Aëtius. The important passage in De somniis 1.21–32 demonstrates his knowledge and direct use of an earlier form of this work. Elsewhere too Philo has used the systematizing method of this form of handbook literature to organize his reports on philosophical questions. In my paper I will explain how the method works, analyse the above-mentioned and other passages, and demonstrate its usefulness for Philo in his exegetical and apologetic enterprise.