The ancient mystics of the galaxy
The ancient mystics of the galaxy have long studied the omnipresent nature of the Force. These scholars and philosophers discovered that the Force was the essence of the universe's cycle of existence, part of life and death in nature. All things in existence are a part of it, but none so much as living, sapient beings. They further learned that with years of patient study, the Force could eventually be manipulated by individuals in a way that defied rational explanations. Because the Force is everywhere, there are no limits to the feats that could be achieved if the being using the Force was knowledgable enough of its way. Beings could communicate across vast distances, heighten their senses and see past the veils of time.
These learned ones preserved their knowledge and established traditions to train their descendants and increase their understanding. These great traditions of enlightenment came to flourish across the galaxy. Many of them focused on particular qualities of the Force or on different disciplines that were but one of many ways of knowing the Force. Still, most of these scholars do agree on basic principles. To better understand the ways of the Force, these scholars characterized it by its two most fundamental aspects: the Light Side and the Dark Side.
The Light is positive. It is intimately bound with the essence of living things; it is peace, harmony, and knowledge. The Light Side springs from the great pattern of existence. It draws strength from diversity and tolerance. It is also inherently communal in nature, thriving on cooperation. Those emotions that enhance the existence of the whole flow from it and tap into its great reserves of strength and peace. Patience, humility, and self-sacrifice are paths to enlightenment. Above all, it seeks harmony and perfection.
The Dark Side, in comparison, is the force of entropy and destruction. Chaos and rage feed it and are its sources of power. The Dark Side is a part of nature--it is not inherently evil, but evil comes from its irrationality, its intolerance, and its lack of control. Bestial and predatory, domination is its goal.
Mercilessly aggressive and unforgiving, its adherents are blinded by greed and lust for power over those weaker than themselves.
The Light and Dark Side manifest themselves in the way they are used; they are simply different interpretations of a single aspect of nature, and they exist in balance with themselves and the universe.
Just as with any aspect of life and death, both the Dark Side and the Light Side are intertwined with each other, are necessary to each other and form a cosmic balance. The important matter is avoiding the emotions of anger and hate which summon the Dark Side. By concentration, it is possible to go beyond desire and emotion, and thereby grow very powerful in the Light Side of the Force. Then great things are possible.