The chronology of Philo's writings is as uncertain as the chronology of his life. Yet it is possible to trace a deepening of outlook and an increasing originality, if we work our way up from the sixth to the first division of the classification. It does not follow that the works were written in this order--and it may well be that Philo was producing at one and the same time books of several classes--but we may use this order as an ideal scale by which to mark off the stages of his philosophical progress. In the first place come the [Greek: Hypotheticha], or apologetic works, which have a practical purpose. With these we may associate the moralizing history that dealt in five books respectively with the persecutions of Sejanus, Flaccus, and Caligula, the ill-starred embassy, and the final triumph of the Jews over their enemies. The [Greek: Hypotheticha] proper, as we gather from Eusebius, contained a general apology for Judaism, and an account of the Essenes--which have disappeared--and the suspected book on the Therapeutic sect known by the title "On the Contemplative Life." Whether they received this generic name because they are suggestions for the Jewish cause, or because they are written to answer the insinuations ([Greek: kath' hypothesin]) of adversaries, is a moot point. But their general purport is clear: they were an apologetic presentation of Jewish life, written to show the falsity of anti-Semitic calumnies. The Jews are good citizens and their manner of life is humanitarian. The Essene sect is a living proof of Jewish practical socialism and practical philosophy, the Therapeutae show the Jewish zeal for the contemplative life. Next we come to Philo's philosophical monographs, which are not, as one might expect, the work of his mature thought, but rather the exercises of youth. Dissertations or declamations upon hackneyed subjects were part of the regular course of the university student at Alexandria, and Philo prepared himself for his Jewish philosophy by composing in the approved style essays upon "Providence," "The Liberty of the Good," and "The Slavery of the Wicked," etc. What chiefly distinguishes them above other collections of commonplaces is the appeal to the Bible for types of goodness, and here again the Essenes figure as the type of the philosophical life.[86] The writer, while still engaged in the studies of the Greek university, is feeling his way towards his system of universal Mosaism.