I have made these remarks in reply to the charges which Celsus and others bring against the simplicity of the language of Scripture, which appears to be thrown into the shade by the splendour of polished discourse. For our prophets, and Jesus Himself, and His apostles, were careful to adopt a style of address which should not merely convey the truth, but which should be fitted to gain over the multitude, until each one, attracted and led onwards, should ascend as far as he could towards the comprehension of those mysteries which are contained in these apparently simple words.
For, if I may venture to say so, few have been benefited (if they have indeed been benefited at all) by the beautiful and polished style of Plato, and those who have written like him; while, on the contrary, many have received advantage from those who wrote and taught in a simple and practical manner, and with a view to the wants of the multitude. It is easy, indeed, to observe that Plato is found only in the hands of those who profess to be literary men; while Epictetus is admired by persons of ordinary capacity, who have a desire to be benefited, and who perceive the improvement which may be derived from his writings.
Now we make these remarks, not to disparage Plato (for the great world of men has found even him useful), but to point out the aim of those who said: “And my speech and my preaching was not with enticing words of man's wisdom, but in demonstration of the Spirit and of power, that our faith should not stand in the wisdom of men, but in the power of God.” For the word of God declares that the preaching (although in itself true and most worthy of belief) is not sufficient to reach the human heart, unless a certain power be imparted to the speaker from God, and a grace appear upon his words; and it is only by the divine agency that this takes place in those who speak effectually.
The prophet says in the sixty-seventh Psalm, that “the Lord will give a word with great power to them who preach.” If, then, it should be granted with respect to certain points, that the same doctrines are found among the Greeks as in our own Scriptures, yet they do not possess the same power of attracting and disposing the souls of men to follow them. And therefore the disciples of Jesus, men ignorant so far as regards Grecian philosophy, yet traversed many countries of the world, impressing, agreeably to the desire of the Logos, each one of their hearers according to his deserts, so that they received a moral amelioration in proportion to the inclination of their will to accept of that which is good.
Source: Against Celsus (New Advent)