God is the one who brings order and purpose to everything. That’s what this is all about.
When God said, “Let there be light,” we must understand it as, “Let there be a period of light.” The author isn’t concerned about what we know from physics to be light, that is, light as a physical entity and with physical properties. “Day One” of creation concerns something far more significant than that—something much more basic to the functioning of the cosmos and our experience of it. God here is creating time. This is the first of the functions that God is going to use to bring order to the chaos: the orderly and regular progression of time.
The people in that day probably viewed light as having existed prior to this statement. They would not have viewed the sun, moon, and stars as the sole source of light, but they certain recognized their role, as in v. 14. They didn’t know that the moon reflected the light of the sun. There is no hint in ancient writings that they knew “daylight” was caused by sunlight, because daylight was present even when the sun was behind a cloud. But the text doesn’t concern itself with the “things” of creation—only the functions and purposes needed for it to operate.
What we’re seeing here, and reading, is the sequence of light and darkness. In verse 5 the light is called “day,” not “light,” and the darkness is called night. The physicist’s light cannot be separated from darkness, but alternating periods of light and darkness can be set up. God is creating time, and time brings purpose, order, and structure to life.
This is written in great contrast to the Babylonian, Egyptian, and Mesopotamian tales, where day and night were warring partners. Instead of cosmic monsters and epic battles, God speaks a word and gives purpose and meaning to what was there. You’re not to picture that suddenly the lights turned on with a pop; remember, we are talking about function here, not structure. God isn’t creating anything. He is bringing order.