In the second and third centuries A.D. Alexandria was the meeting-point of three distinct cultural streams, namely the Jewish-Alexandrine philosophy, Platonism, and Gnosticism, all of which had an influence on Alexandrine orthodox Christianity. Starting from the assumption that the thought of a Christian Father like Clement of Alexandria cannot be fully understood without taking this influence into account, the author examines in detail Clement\'s close dependence on the Jewish-Alexandrine philosophy, Middle Platonism, Neoplatonism, and Gnosticism in such matters as his attitude towards Greek philosophy, ethics, his views on \'pistis\' and \'gnosis\', cosmology and theology. Particular attention has been paid to the Gnostic texts from Nag-Hammadi so far published.