Jesus went on to make two points about light. First, you can't miss it. Just like cities always glow in the dark at night, we cannot reflect his light and remain obscure. We cannot live light filled lives in our society without standing out, without having people notice us. They may not like us, and they may persecute us, but they will know we are there. God didn't call us into the Secret Service; he called us to spread the light everywhere.
Second, you use light to help people see. The only way for people to see clearly what matters is for us to become light. We are to bring the light of the gospel and the light of Christian character to the world around us. Now our natural tendency is to withdraw from the blackness of this world and to simply shine our lights in our churches or with our Christian friends. We all gather together like one magnificent chandelier to admire each other's lights. And that's good in and of itself, but God has called us to much more than that. He has called us to be a single light bulb in the back hall to keep people from breaking their necks when they go to the bathroom in the middle of the night. He has called us to make a difference in the darkness. The blacker the night is around us, the greater the need for our light bulb. Your lost friends and the world around you needs your light. So let it shine.
On June 5, 1910, American short story writer O. Henry spoke his last words: "Turn up the lights -- I don't want to go home in the dark." As lights in the world, our mission is to make sure no one ever does - that no one ever goes home in the dark.