Originally Posted by
Mimilu
It's less complicated then that.
In Final Fantasy 3, there are two "worlds", The Floating Continent (referred to as the World of Light) and the Surface World (referred to as the World of Darkness).
Now, both Light and Darkness have an evil personification, that show up when there is an imbalance, that want to fling the whole world into their respected element, which in turn will reduce the world to nothingness, all darkness or all light.
Each world has warriors and four crystals to protect it.
It's not so much as Light = Good, Darkness = Bad but that their are elements just like Fire and Water or Earth and Wind.