Celsus quotes another saying of Plato to the following effect: “It has occurred to me to speak once more upon these subjects at greater length, as perhaps I might express myself about them more clearly than I have already done for there is a certain 'real' cause, which proves a hindrance in the way of him who has ventured, even to a slight extent, to write on such topics; and as this has been frequently mentioned by me on former occasions, it appears to me that it ought to be stated now.
In each of existing things, which are necessarily employed in the acquisition of knowledge, there are three elements; knowledge itself is the fourth; and that ought to be laid down as the fifth which is both capable of being known and is true. Of these, one is 'name;' the second is 'word;' the third, 'image;' the fourth, 'knowledge.'” Now, according to this division, John is introduced before Jesus as the voice of one crying in the wilderness, so as to correspond with the “name” of Plato; and the second after John, who is pointed out by him, is Jesus, with whom agrees the statement, “The Word became flesh;” and that corresponds to the “word” of Plato.
Plato terms the third “image;” but we, who apply the expression “image” to something different, would say with greater precision, that the mark of the wounds which is made in the soul by the word is the Christ which is in each one of us and this mark is impressed by Christ the Word. And whether Christ, the wisdom which is in those of us who are perfect, correspond to the “fourth” element— knowledge— will become known to him who has the capacity to ascertain it.
Source: Against Celsus (New Advent)