Chapter XVIII.--The Use of Philosophy to the Gnostic.
Greek philosophy the recreation of the Gnostic.
Now our Gnostic always occupies himself with the things of highest importance. But if at any time he has leisure and time for relaxation from what is of prime consequence, he applies himself to Hellenic philosophy in preference to other recreation, feasting on it as a kind of dessert at supper.  Not that he neglects what is superior; but that he takes this in addition, as long as proper, for the reasons I mentioned above. But those who give their mind to the unnecessary and superfluous points of philosophy, and addict themselves to wrangling sophisms alone, abandon what is necessary and most essential, pursuing plainly the shadows of words.
It is well indeed to know all. But the man whose soul is destitute of the ability to reach to acquaintance with many subjects of study, will select the principal and better subjects alone. For real science (episteme, which we affirm the Gnostic alone possesses) is a sure comprehension (katalepsis), leading up through true and sure reasons to the knowledge (gnosis) of the cause. And he, who is acquainted with what is true respecting any one subject, becomes of course acquainted with what is false respecting it.
For truly it appears to me to be a proper point for discussion, Whether we ought to philosophize: for its terms are consistent.
But if we are not to philosophize, what then? (For no one can condemn a thing without first knowing it): the consequence, even in that case, is that we must philosophize. 
First of all, idols are to be rejected.
Such, then, being the case, the Greeks ought by the Law and the Prophets to learn to worship one God only, the only Sovereign; then to be taught by the apostle, "but to us an idol is nothing in the world,"  since nothing among created things can be a likeness of God; and further, to be taught that none of those images which they worship can be similitudes: for the race of souls is not in form such as the Greeks fashion their idols. For souls are invisible; not only those that are rational, but those also of the other animals. And their bodies never become parts of the souls themselves, but organs--partly as seats, partly as vehicles--and in other cases possessions in various ways. But it is not possible to copy accurately even the likenesses of the organs; since, were it so, one might model the sun, as it is seen, and take the likeness of the rainbow in colours.
After abandoning idols, then, they will hear the Scripture, "Unless your righteousness exceed the righteousness of the scribes and Pharisees"  (who justified themselves in the way of abstinence from what was evil),--so as, along with such perfection as they evinced, and "the loving of your neighbour," to be able also to do good, you shall not "be kingly." 
For intensification of the righteousness which is according to the law shows the Gnostic. So one who is placed in the head, which is that which rules its own body--and who advances to the summit of faith, which is the knowledge (gnosis) itself, for which all the organs of perception exist--will likewise obtain the highest inheritance.
The primacy of knowledge the apostle shows to those capable of reflection, in writing to those Greeks of Corinth, in the following terms: "But having hope, when your faith is increased, that we shall be magnified in you according to our rule abundantly, to preach the Gospel beyond you."  He does not mean the extension of his preaching locally: for he says also that in Achaia faith abounded; and it is related also in the Acts of the Apostles that he preached the word in Athens.  But he teaches that knowledge (gnosis), which is the perfection of faith, goes beyond catechetical instruction, in accordance with the magnitude of the Lord's teaching and the rule of the Church.  Wherefore also he proceeds to add, "And if I am rude in speech, yet I am not in knowledge." 
Whence is the knowledge of truth?
But let those who vaunt on account of having apprehended the truth tell us from whom they boast of having heard it. They will not say from God, but will admit that it was from men. And if so, it is either from themselves that they have learned it lately, as some of them arrogantly boast, or from others like them. But human teachers, speaking of God, are not reliable, as men. For he that is man cannot speak worthily the truth concerning God: the feeble and mortal [cannot speak worthily] of the Unoriginated and Incorruptible--the work, of the Workman. Then he who is incapable of speaking what is true respecting himself, is he not much less reliable in what concerns God? For just as far as man is inferior to God in power, so much feebler is man's speech than Him; although he do not declare God, but only speak about God and the divine word. For human speech is by nature feeble, and incapable of uttering God. I do not say His name. For to name it is common, not to philosophers only, but also to poets. Nor [do I say] His essence; for this is impossible, but the power and the works of God.
Those even who claim God as their teacher, with difficulty attain to a conception of God, grace aiding them to the attainment of their modicum of knowledge; accustomed as they are to contemplate the will [of God] by the will, and the Holy Spirit by the Holy Spirit. "For the Spirit searches the deep things of God. But the natural man receiveth not the things of the Spirit." 
The only wisdom, therefore, is the God-taught wisdom we possess; on which depend all the sources of wisdom, which make conjectures at the truth.
Intimations of the Teacher's advent
Assuredly of the coming of the Lord, who has taught us, to men, there were a myriad indicators, heralds, preparers, precursors, from the beginning, from the foundation of the world, intimating beforehand by deeds and words, prophesying that He would come, and where, and how, what should be the signs. From afar certainly Law and Prophecy kept Him in view beforehand. And then the precursor pointed Him out as present. After whom the heralds point out by their teaching the virtue of His manifestation.
Universal diffusion of the Gospel a contrast to philosophy.
The philosophers, however, chose to [teach philosophy] to the Greeks alone,  and not even to all of them; but Socrates to Plato, and Plato to Xenocrates, Aristotle to Theophrastus, and Zeno to Cleanthes, who persuaded their own followers alone.
But the word of our Teacher remained not in Judea alone, as philosophy did in Greece; but was diffused over the whole world, over every nation, and village, and town, bringing already over to the truth whole houses, and each individual of those who heard it by him himself, and not a few of the philosophers themselves.
And if any one ruler whatever prohibit the Greek philosophy, it vanishes forthwith.  But our doctrine on its very first proclamation was prohibited by kings and tyrants together, as well as particular rulers and governors, with all their mercenaries, and in addition by innumerable men, warring against us, and endeavouring as far as they could to exterminate it. But it flourishes the more. For it dies not, as human doctrine dies, nor fades as a fragile gift. For no gift of God is fragile. But it remains unchecked, though prophesied as destined to be persecuted to the end. Thus Plato writes of poetry: "A poet is a light and a sacred thing, and cannot write poetry till he be inspired and lose his senses." And Democritus similarly: "Whatever things a poet writes with divine afflatus, and with a sacred spirit, are very beautiful." And we know what sort of things poets say. And shall no one be amazed at the prophets of God Almighty becoming the organs of the divine voice?
Having then moulded, as it were, a statue of the Gnostic, we have now shown who he is; indicating in outline, as it were, both the greatness and beauty of his character. What he is as to the study of physical phenomena shall be shown afterwards, when we begin to treat of the creation of the world.