Iulianus Augustus: Oration VI - To the Uneducated Cynics; The Works of the Emperor Julian II, transl. W.C. Wright; Loeb 1913

Further, that to make oneself like God as far as possible is nothing else than to acquire such knowledge of the essential nature of things as is attainable by mankind, is evident from the following. It is not on the score of abundance of possessions that we count the divine nature happy, nor on the score of any other of those things that are commonly believed to be advantages, but it is because, as Homer says, "The gods know all things"; and indeed he says also of Zeus, “But Zeus was older and wiser."  
For it is in knowledge that the gods surpass ourselves. And it may well be that with them also what ranks as noblest is self-knowledge. In proportion then as they are nobler than we in their essential nature, that self-knowledge of theirs is a knowledge of higher things. Therefore, I say, let no one divide philosophy into many kinds or cut it up into many parts, or rather let no one make it out to be plural instead of one. For even as truth is one, so too philosophy is one. But it is not surprising that we travel to it now by one road, now by another. For if any stranger, or, by Zeus, anyone of her oldest inhabitants wished to go up to Athens, he could either sail or go by road, and if he travelled by land he could, I suppose, take either the broad highways or the paths and roads that are short cuts. And moreover he could either sail along the coasts or, like the old man of Pylos, "cleave the open sea." And let no one try to refute me by pointing out that some philosophers in travelling by those very roads have been known to lose their way, and arriving in some other place have been captivated, as though by Circe or the Lotus-Eaters, that is to say by pleasure or opinion or some other bait, and so have failed to go straight forward and attain their goal. Rather he must consider those who in every one of the philosophic sects did attain the highest rank, and he will find that all their doctrines agree. 
Therefore the god at Delphi proclaims, "Know Thyself," and Heracleitus says, "I searched myself" ; and Pythagoras also and his school and his followers down to Theophrastus, bid us become like God as far as possible, yes and Aristotle too. For what we are sometimes, God is always. It would therefore be absurd that God should not know himself. For he will know nothing at all about other things if he be ignorant of himself. For he is himself everything, seeing that in himself and near himself he keeps the causes of all things that in any way whatever have existence, whether they be immortal causes of things immortal, or causes of perishable things, though themselves not mortal or perishable; for imperishable and ever-abiding are the causes of perpetual generation for the perishable world. But this line of argument is too lofty for the occasion.