The remark, indeed, was true which Celsus made, that any one, on hearing his words, would answer, seeing that his words are words of darkness, “You pour darkness before my eyes.” Celsus verily, and those like him, do desire to pour darkness before our eyes: we, however, by means of the light of the Word, disperse the darkness of their impious opinions. The Christian, indeed, could retort on Celsus, who says nothing that is distinct or true, “I see nothing that is distinct among all your statements.”
It is not, therefore, “out of darkness” into “the brightness of light” that Celsus leads us forth: he wishes, on the contrary, to transport us from light into darkness, making the darkness light and the light darkness, and exposing himself to the woe well described by the prophet Isaiah in the following manner: “Woe unto them that put darkness for light, and light for darkness.” But we, the eyes of whose soul have been opened by the Word, and who see the difference between light and darkness, prefer by all means to take our stand “in the light,” and will have nothing to do with darkness at all.
The true light, moreover, being endued with life, knows to whom his full splendours are to be manifested, and to whom his light; for he does not display his brilliancy on account of the still existing weakness in the eyes of the recipient. And if we must speak at all of “sight being affected and injured,” what other eyes shall we say are in this condition, than his who is involved in ignorance of God, and who is prevented by his passions from seeing the truth? Christians, however, by no means consider that they are blinded by the words of Celsus, or any other who is opposed to the worship of God.
But let those who perceive that they are blinded by following multitudes who are in error, and tribes of those who keep festivals to demons, draw near to the Word, who can bestow the gift of sight, in order that, like those poor and blind who had thrown themselves down by the wayside, and who were healed by Jesus because they said to Him, “Son of David, have mercy upon me,” they too may receive mercy and recover their eyesight, fresh and beautiful, as the Word of God can create it.
Source: Against Celsus (New Advent)