Light is a person, God himself. Darkness is impersonal, the rejection of the light. Because the premise of his kingdom is that every member of it may be his own god, satan has no true subordinates. More contrasts between light and darkness. Light possesses its own real power, darkness only illusory power.
Light is living, darkness is dead.
Light overcomes darkness. The light, which is self-existent, possesses its power in and of itself. Light grows and produces living fruit - goodness, righteousness and truth. Darkness produces only dead, unfruitful works. Light and truth are allies, as are darkness and the lie.