A rough contemporary of Jesus, Philo of Alexandria had enormous influence on the development of religious thought not only among his fellow Jews, but in Christianity and Islam as well. Yet he's little known, except among specialists.
Philo Judaeus, as he's sometimes called, received a superb education in Greek literature and philosophy and rose to prominence in the large Jewish community of ancient Alexandria. He dedicated his life to the service and defense of Judaism. Indeed, in A.D. 40 he was chosen to lead a Jewish delegation to Rome, where he appealed to the emperor Caligula to intervene on behalf of Egyptian Jews who were being persecuted by their Gentile neighbors and leaders.
But Philo's real interests weren't political. He sought to defend Judaism against the charge of sophisticated pagans that it was primitive and backward. This he did by writing a vast, multi-volume commentary on what we now know as the Old Testament, in which he attempted to show that, in fact, all of the wisdom and insight of Greek philosophy — which was the most prestigious thinking, the elite ideology and "science," of his day — actually originated in the writings of Moses.
Philo seems to have read the Bible only in Greek. And he did so using an allegorical technique that he borrowed from the leading scholars of his homeland, pagan Hellenistic Egypt. These pagan intellectuals were embarrassed by the rather crude stories about the gods they found (especially but not only) in their beloved Homer, and they wanted to save that poet from himself.
Philo, likewise, was plainly embarrassed by some of what he found in scripture. Among the things he particularly disliked, being a devout disciple of Plato, was the notion that God might have a physical body.
Thus, Philo read the stories and rules of the Bible as allegories that really taught — surprise! — the philosophy of Plato and Aristotle. The historical personalities and events described in Jewish scripture faded into relative insignificance and became, under his hands, personifications of abstract ideas and ethical virtues. The ancient Hebrew prophets, it turned out, were really Middle Platonic philosophers.
Philo was among the principal developers of what is today known as "negative theology." According to this approach, we can or should say nothing positive about God. We shouldn't call him "just," for instance, since that would seem to mean that his justice has some kinship to human justice. We shouldn't call him "wise," for his wisdom is utterly different from ours. We should only deny that he is unjust, and say that he isn't unwise. In this way, by removing attributes from God in much the way that a sculptor chips away marble from his statue, we can eventually reach a quite accurate notion of God by knowing completely what he isn't.
Another doctrine associated with Philo is that of the "Logos," or (as it's commonly but inadequately translated) the "Word." (This same term appears in the first chapter of the gospel of John.) Philo's God was so exalted above human conceptions, so transcendent, that Philo was obliged to speak of an intermediate divine being, the Logos, who connected that distant God with us and with the world in which we live. Scholars debate whether Philo invented this idea, or whether he was reflecting much more ancient Jewish notions of a secondary God who was subordinated to the higher God like a son to a father. The British Methodist biblical scholar Margaret Barker contends that the Jews who accepted Jesus as divine were largely those who "remembered" this ancient Hebrew doctrine of a divine Son.
Philo seems to have had no disciples among Jews in his own day, but his impact on Christianity may have been enormous. It's probably no coincidence that Clement and Origen of Alexandria, when they opened their famous Christian school there in the third century, applied the tools of allegorical interpretation to the Bible to neutralize its anthropomorphisms and other embarrassments. And, later, after the rise of Islam, Philo's style of allegorizing became very influential among Muslims — particularly among the Shi'ite sect known as the Isma'ilis, who, in the form of the medieval Fatimid dynasty, ruled Egypt for approximately two centuries.
If Judaism, Christianity and Islam are all offspring of Abraham, they're also — in today's mainstream varieties, anyway — the descendants of a relatively little known Egyptian named Philo.