Darkness and Light, for the most part are broad concepts, but really they are perspectives that each individual has on the matter. Some say Darkness is evil, Light is good, but what is truly right and wrong? What is truly good and evil? Just questions I believe there is no true answer. It's based on morals, a majority of beings having a very similar belief on what is what. That's the way we have determind things, by a majority of people sharing a similar belief. Now, not everyone agrees, thus concepts are born, but it all starts with and idea or a thought, then a perception, then based on the perception comes opinion, and then if the opinion is strong enough and others accept the opinion is legitimate and has facts to back it up, it becomes a theory, then if that theory is not proved wrong and it stands the test of time it becomes a law.
Everything begins with a thought, impulses, they are subconscious thoughts that are not on the conscious, but they trigger a reaction, but it still starts from a thought or an idea, like everything else.