John 1:4 In Him was life, and the life was the light of men.Psalm 36:9 For with thee [is] the fountain of life: in thy light shall we see light.
Knowledge is absolutely different from light. Those who have light surely have the knowledge, but those who have knowledge do not necessarily have light. There is a big difference between a blind man's knowledge of colors and a child's experience of them. A blind man may have the knowledge of colors, but he has never seen them. A child may not have the knowledge of colors, but he knows what colors are from his experience. It is a pity that believers today pay so much attention to knowledge instead of light.
The realization of sin is not a question of knowledge but a question of light. A student once said to Mr. Bengal, a famous Bible expositor, "I have recently discovered the doctrine of sin from the book of Romans." Mr. Bengal looked at him and said, "Do you mean to tell me that today is the first time that you have known about the doctrine of sin? By now you should have realized that your whole person is sin from your daily experience!"
In order to receive God's light, we have to draw near to God. We must be one who is near God, and one who draws nigh to Him, because only God is light. He is the source of light. When we are near Him and when we draw nigh to Him, we receive light.