C. S. Lewis explained his belief in Christ in this way: "I believe in Christianity as I believe that the Sun has risen, not only because I see it, but because by it I see everything else" (Lewis, Is Theology Poetry?, 1945). Christ said, "I am the light of the world, he that followeth me shall not walk in darkness..." (John 8:12). Christ also said, "Ye are the light of the world...let your light so shine before men, that they may see your good works..." (Matt. 5:14,16). What is this light? Did Christ mean that He was merely a physical light, an electromagnetic radiation that brightens the world around us? It is true that Jesus Christ shines with a radiance above the brightness of the sun, as Joseph Smith described. But this is not really what Christ meant when He stated that He (and, by our following His example and through His spirit, we as well) is the light of the world. Christ is more than electromagnetic energy; He is more powerful and deeper than this physical light.
One powerful source of energy is love. Love is energy, you can feel it - it radiates like the sun. Jesus is "the light of the world"; He created the earth, the moon, and the heavens above. He caused the sun to shine upon the earth to give us life. Jesus lights the earth around us but He also does more than that - He lights our souls with His love. Christ is love. When we are told to "let [our] light[s] so shine" the Savior is telling us to follow His example by lighting others' lives by love; we are to warm the hearts and souls of all humankind through the warm radiance of charity. When we follow our Lord by keeping His commandments, He lights our souls with His love. When we have His love, we can share it with others. This means that it is not possible to light someone else's soul without a burning in your own. This is a light that is in all people's souls. In some it burns with a dazzling brightness, in others it flickers like a dying candle, but it is there. C. S. Lewis said, "[We are] in a society of possible gods and goddesses...[in which] there are no ordinary people. [We] have never talked to a mere mortal. Nations, cultures, arts, civilisations - these are mortal, and their life is to ours as the life of a gnat. But it is immortals whom we joke with, work with, marry, snub, and exploit." (Lewis, The Weight of Glory). When we have charity we keep in perspective who those around us really are - we are all sons and daughters of our Eternal Father in Heaven. We have His divine spark within us. We all have the potential to become as He is.
But that is a process - the becoming as God is. None of us is perfect; people are not perfect. We are in an embryonic stage, trying to grow up and control these wonderful, mortal, physical bodies the Lord blesses us with. As premortal beings, all of us here on this earth as mortals subjected our spiritual bodies and wills to the will of the Father; that is why we are here in mortality - we accepted the opportunity to follow God's plan for us. Now as mortals we are trying to subject our physical bodies to the will of the Father, a difficult task at which we much work each day. Once again Christ was the consummate example. His will was completely in subjection to His Father's, which subjection culminated with His death on the cross and His triumphal resurrection from the tomb.