Originally posted by Spelljammer
The only thing that is polar is The Force, and this is how we differ in what to do with it, and which polarity to draw energy from..
But the Force isn't polar. The Dark Side and the Light Side cannot be at opposite ends of an absolute spectrum, or else Luke could not have been able to use the Grip and remain a Jedi, as the Grip has been clearly labeled as a Dark Side power.
If it weren't for the Sith themselves referring to "The Dark Side" of the Force, I would have to say that the two Sides were an arbitrary belief set upon a whole by the Jedi.