The book of Genesis begins with God’s separation of the light from the dark. This separation originates in the cosmos, but it describes man’s moral state in the Old Testament and the New Testament. Light is assigned the good, and darkness is assigned the evil. In Isaiah 5:20, the prophet warns, "Woe unto them that call evil good, and good evil; that put darkness for light, and light for darkness; that put bitter for sweet, and sweet for bitter.” In this sense, light becomes God's absolute law, and darkness the unequivocal rejection of that law.
Light as Love
In classical literature, light is often synonymous with love, especially the overwhelming power of the physical emotion. As light can blind, so can love. Perhaps the most notable example of this use is evident in William Shakespeare’s “Romeo and Juliet,” which relies heavily on the symbol of light to describe the emotional state of the young lovers. In the famous balcony scene of Act 2, Romeo first sees Juliet as the sun itself, as the ultimate source of life: “But soft, what light through yonder window breaks? / It is the east and Juliet is the sun!" Sun, moon and star metaphors appear throughout the play, evoking love's illuminating, sometimes bewildering power.
Muddling Light and Dark
Authors have played with the distinctions of light and dark for as long as others have reinforced their separateness. The romantics and existentialists viewed darkness as a necessary condition of life -- not only essential to any true fullness of being, but also essential to human freedom. Darkness, in a way, became the space in which man faced his greatest horrors and determined his own fate. In Act 3 of Lord Byron’s metaphysical drama “Manfred,” the protagonist proclaims “the night / Hath been to me a more familiar face / Than that of man; and in her starry shade / Of dim and solitary loveliness, / I learn’d the language of another world.” Darkness not only comforts Manfred but educates him as well.
Light and dark symbolism still thrives in contemporary literature. One of the greatest employers of the dichotomy is American author Cormac McCarthy. At the end of his novel “All the Pretty Horses,” the young hero, John Grady Cole, rides his horse through the barren landscape until their tandem shadows “passed and paled into the darkening land, the world to come." As in many of his stories set along the U.S.-Mexico border, McCarthy describes the past as a lighted world fading into a cold, dark future.