Celsus next refers us to Plato as to a more effective teacher of theological truth, and quotes the following passage from the Timæus: “It is a hard matter to find out the Maker and Father of this universe; and after having found Him, it is impossible to make Him known to all.” To which he himself adds this remark: “You perceive, then, how divine men seek after the way of truth, and how well Plato knew that it was impossible for all men to walk in it. But as wise men have found it for the express purpose of being able to convey to us some notion of Him who is the first, the unspeakable Being—a notion, namely; which may represent Him to us through the medium of other objects—they endeavour either by synthesis, which is the combining of various qualities, or by analysis, which is the separation and setting aside of some qualities, or finally by analogy—in these ways, I say, they endeavour to set before us that which it is impossible to express in words.
I should therefore be surprised if you could follow in that course, since you are so completely wedded to the flesh as to be incapable of seeing ought but what is impure.” These words of Plato are noble and admirable; but see if Scripture does not give us an example of a regard for mankind still greater in God the Word, who was “in the beginning with God,” and “who was made flesh,” in order that He might reveal to all men truths which, according to Plato, it would be impossible to make known to all men, even after he had found them himself.
Plato may say that “it is a hard thing to find out the Creator and Father of this universe;” by which language he implies that it is not wholly beyond the power of human nature to attain to such a knowledge as is either worthy of God, or if not, is far beyond that which is commonly attained (although if it were true that Plato or any other of the Greeks had found God, they would never have given homage and worship, or ascribed the name of God, to any other than to Him: they would have abandoned all others, and would not have associated with this great God objects which can have nothing in common with Him). For ourselves, we maintain that human nature is in no way able to seek after God, or to attain a clear knowledge of Him without the help of Him whom it seeks.
He makes Himself known to those who, after doing all that their powers will allow, confess that they need help from Him, who discovers Himself to those whom He approves, in so far as it is possible for man and the soul still dwelling in the body to know God.
Source: Against Celsus (New Advent)