Philo’s ideas about the knowledge of God seem to belong to the tradition of apophatic theology, which for him is grounded both in Scripture and in Plato, who famously proclaimed the divinity to be difficult to know and impossible to express. The Platonic foundation may explain the reason why some aspects of this approach are very similar in Philo, Plotinus, Origen, Gregory Nyssen, and Evagrius, all Platonists from different religions. Besides Plato, The roots of Philo’s apophaticism are found in his Biblical exegesis. Philo interpreted some biblical episodes as the allegorical expression of the necessity of apophaticism: this meant the awareness of the limit of human cognitive and discursive-expressive power when it came to the divinity in itself, that is, its nature or essence as distinct from its activities and their products. This presupposed a transcendent notion of the divinity, which squares with Platonism but not with an immanentistic system such as Stoicism. These allegorical expressions appear precisely in passages which can be fruitfully compared with the parallel interpretations of Origen and Nyssen. I shall analyze how Philo grounded his tenet that, because of its transcendence, the divinity is unknowable in its essence (??s?a), and therefore also ineffable, but knowable through its activity. Even the epithets that are ascribed to God in the Bible do not reveal God’s very essence but God’s relationship to the creation. What humans can know about God is that God is, but not what God is. Divine revelation in Scripture moderates negative theology, but is also subject to strict rules of interpretation. Allegoresis is the key to grasping the true meaning of the Bible, but it is also a key available to few, those who master this hermeneutical tool. However difficult, the search for God is, according to Philo, the noblest among human activities. ?hus, the cognitive impairment of human beings before the divine should not stop their “theo-logical” investigation. Philo and the (Platonic) apophatic theologians who followed him show a tension between apophaticism and the discourse on God that they did nevertheless pursue. Te?????a means reasoning and speaking (?????) about the divine (?e??), but if the divine is unknowable, how can theology work? This is why Philo opted for the strategy of differentiation: the divine’s intimate nature/essence is inaccessible, but manifests itself in its activities. This strategy proved immensely influential on later Christian Platonism. For the Christian Platonists, however, apophaticism and its counterpart, mysticism, have also an eschatological dimension as anticipation of the final restoration and deification. This dimension may be lacking in Philo, as will be discussed in this paper. This obviously bears on the issue of Philo’s elusive view of the end.