In Hebraic-Christian thought it is usually taken for granted that God has his name. But in Philo's writings there is found an argument that the deity being incomprehensible and ineffable cannot have a name. As Professor H. A. Wolfson has pointed out, this thought cannot be accounted for simply by tracing it back to Plato and Aristotle. It should rather be regarded as a product of the encounter between Hebraism and Hellenism in the milieu of the first-century Alexandria. Our task then is to examine how much Hellenization there resulted or how successful Philo was in interpreting his Hebraic faith in terms of Greek philosophy. On the basis of the Greek version of Exodus 3 : 14 Philo identified God with to on and thus introduced the ontologioal way of thinking into his exegesis of the Pentateuch. He may indeed be called the father of ontological theology. But the original Hebrew words of the text, 'ehyeh 'asher 'chyeh, does not exactly mean that the deity is being. The verb hayah is a pregnant term meaning ' to happen" and "to become" as well as "to be". Accordingly we might characterize the Hebraic way of thinking as hayathological in contradistinction to Greek ontology. The hayathological deity concerns man not abstractly but personally and concretely in a historic situation. Philo indeed tries to show that his God as absolutely incomprehensible is more than the Platonic to on. But he fails to do full justice to Hebrew hayathology when he argues that God has simply no name, for it is tantamount to saying that God is after all abstract being. When Professor Paul Tillich says that God is "being" or ' the ground of being" while "living God" is only a symbolic designation, his thought still moves along the Philonic lines. We are confronted here with the same sort of ditficulty as we find in the Jewish philosopher of the first century.