In the Katha Upanishad it is said of the self: “Him the sun does not illumine, nor the moon, nor the stars, nor the lightning–nor, verily, fires kindled upon the earth. He is the one light that gives light to all. He shining, everything shines.” The self is illumined by no external light, but rather illumines all itself.
We could shine the brightest of lights into the eyes of a dead man and he would see nothing. But if the self is present to enliven him, then he will. The self is known–seen–by the self, and therefore it is called swayamprakash: self-illumined. Hence only those in contact with their self can be said to possess illumination to any degree.
Those who under the banner of “devotion” obsess on external practices and deities can only dwell in the “light that is darkness.” We must seek illumination in the self alone, keeping in mind that God is the Self of the self, that to seek one is to seek the other.