Now the way in which Clement did it, with respect to predominantly Stoic ideas and educational principles, we have noted. We now come to Origen and his system.

Here we have the fulfillment of this program. Origen begins his system with the question of the sources. (By the way, his system is the first complete system of Christian theology, even over against Irenaeus and Tertullian). He takes these sources much more seriously than Clement ever did. The sources are the Biblical writings and their summary in the ecclesiastical teaching and preaching. The old “rule of faith” gives the systematic scheme for his system, but the basis of all the contents are the Biblical books. Therefore, as in Clement, Origen says that the first step for the true theologian is the acceptance of the Biblical message. Nobody can be a theologian who does not belong to the congregation; a free-soaring philosopher is not a Christian theologian. But this is not all that is needed. In order to become a theologian, you must also try to understand, and that means, for him, philosophical and especially Neo-Platonic understanding. This is the answer to the same problem, very similar to that of Clement, but as we shall see, much more developed and elaborated and infinitely important for all later Christian development.

Paul Tillich, A History Of Christian Thought – Table of Contents