In John 1:1-4 of the Christian Bible, it says:
In the beginning was the Word, and the Word was
With God, and the Word was God.
The same was in the beginning with God.
All things were made by him; and without him was not
Any thing made that was made.
In him was life; and the life was the light of men.
Here the "light" of men is identified with life. We know what light is—we see natural light every day and artificial light whenever we flip the switch. And we know that sun light is essential to life, but this statement seems to be saying something additional: that life is, or was, "the light of men." "Light" has an alternative meaning, as when we "turn light on the subject" which identifies that aspect of directed consciousness that leads to intelligence about a subject. We see consciousness everywhere, but is it this particular aspect of focused, analytical, consciousness seemingly unique to humans that is the "light of men?"
Life evolves into new forms, but the statement seems to characterize the life of men as different than other life, and relates it to a particular kind of light. We speculate that this "light of men" is that of Soul Consciousness and is the light referred to in the word "Enlightenment."