Often known as Philo Judaeus, philosopher, writer and political leader, was the leading exponent of Alexandrian-Jewish culture, and, together with Josephus, the most significant figure in Jewish-Greek literature. Philo's voluminous works were a formative influence on Neoplatonism and on Christian theology, from the New Testament on. His family was prominent in the Jewish diaspora and in the service of Rome in the east. The two sons of his brother, Alexander the Alabarch, were Marcus Julius Alexander, husband of Julius Agrippa I's daughter Berenice, and Tiberius Julius Alexander. The only fixed date in Philo's own life is ad 39/40, when, as an old man, he led the Jewish embassy to Gaius (1); see section on Gaius and the Jews. Apart from those events, he himself seems to have confined his activities to the Alexandrian Jewish community. He made a pilgrimage to Jerusalem, but need not otherwise have had much contact with Palestine. Virtually all his surviving works were apparently preserved in the library of Caesarea built up by Origen and then by Eusebius, who catalogues most of them at HE 2. 18. Some three-quarters of the corpus consists of exposition of the Pentateuch, in three series, whose order of writing is obscure: Quaestiones, which are brief catechetical commentaries in the form of questions and answers, Legum allegoria, a more extended and systematic exegesis, and Exposition, which sets out the Mosaic laws. The Life of Moses was perhaps a separate enterprise, as also the De vita contemplativa, which describes the way of life of a group of Egyptian Jewish ascetics called the Therapeutai. Two tracts, In Flaccum and the De legatione ad Gaium, probably originally one composite work, give a graphic account of the persecutions of the Jews under Gaius and of their political consequences. The In Flaccum gives much space to the divine punishment inflicted on the persecutors of the Jews.
Philo operated within the Greek philosophical tradition and deployed an elaborate Greek literary language. At the same time, he was at home with the Greek Bible on which his commentaries were based. The sole authority of the Mosaic law was fundamental to him. The spuriousness of his Hebrew etymologies suggests, but does not prove, that he did not know Hebrew. His ontology was markedly Platonic: to provide a medium for the operation of a perfect God upon an imperfect world, he introduced a range of mediating powers, notably dunameis and the logos. Philo's ethics are close to Stoicism, but for him true morality is imitation of the Deity.