Nobody likes pollution; not of any sort.
We prefer clean and fresh. New and unused. In fact, there are some situations where we automatically assume that what we buy or use is pure and clean. There are even situations where the law requires it!
When you pop out to your local fast food joint for a quick bite of lunch, the waitress might ask if you want chips with your burger; but you'll never get the questions, "Did you want a clean plate?" Of course you do !!!! Even getting asked the question would raise serious concerns in your mind about your choice of restaurants, right?
Genesis begins, rightly so, at the beginning of God's creation. God creates the heavens and the earth, but the earth is formless, void and covered in darkness. The first recorded words of God contained in the scriptures are, "Let there be light." His next action is to immediately separate the light from the darkness.
There are things that do not go well together. Oil and water, for example. They refuse to mix naturally. You can shake, mix, blend or do whatever you'd like; but as soon as you stop they'll begin to separate. Pretty soon the oil will be floating atop the water. But there are other things that cannot mix at all.
I remember being in Israel and beginning to learn words and phrases in Hebrew. Sometimes I'd mix them up in pretty strange ways. One morning, I accidentally asked for a drink of "maim sherutim." That's water from the toilet! Obviously, the waitress knew I was mistaken. That's not what I wanted. That's not what ANYBODY wants.
Light never mixes with darkness. When you turn on a light in darkened room, the area around the light becomes, well - LIGHT !!! It always happens that way. You'll never find a big blob of darkness just hovering in the air under a working light bulb. Light dispels darkness.
Jesus says that we are the light of the world. We, as Christians, are His Body and He is our head. It is as though He is walking parts of the earth where He never trod 2000 years ago. Still bringing light, still loving people trapped in darkness. Now as then, He reaches to the sinner, the downtrodden, the lost and the hopeless. He shines a light into their darkness and offers to set them free. The light overcoming the darkness.
Light doesn't mix with or accept darkness. It overcomes it.
God saw that the light was GOOD, so He separated it from the darkness.
Live so that people can see the light of Christ in you.
Let your light so shine before men that they may see your goodness and glorify your Father in heaven.
Let them see Christ in you. Unpolluted. Undiluted.