We know that Dark side is linked to emotion like fear and anger, but the interesting point here is the between line the two side of the force.
As an example, what make Mind tricks a "acceptable" force power for a Jedi? How could you hurt someone, like Obi-Wan does in the Mos Eisley Cantina when he slashed a alien's arm off with his lightsaber, and still be a Jedi?
In the Star Wars Universe, the difference between the light side and dark side is...a gray area.
Essentially, if you are using the Force out of anger, lust, greed, vengeance, or fear, you likely channel the dark side. If you are using the Force to defend you are using the light side.
There are very few techniques which are unambiguously light or dark. The ability to stimulate cellular regeneration ('Force Heal') is generally considered light, but a malicious individual could use it to restore health to a torture victim, for instance, to prepare them for more.
The only truly unique powers to either side are, I believe, Force Choke and Force Lightning. These are unambiguous mainly because they use the Force explicitly to kill. No other power seen uses the force for that purpose, and it can even be seen as mildly damaging to the Force itself to do so (since the Force is generated by life, using it to bring death is abominable).
For the most part, Force powers are tools, neither good nor bad on their own. Their USER is light or dark.
The Force is different things to different cultures:
The Old Jedi Council considered any Force use that requires emotion to be of the dark side, and the light side to be that which requires knowledge and control with the absence of emotion.
Several cultures believe that the Force is magic and that any attempt to use it is evil.
The Sith believe the Force is nothing more than a tool to be used for the wielder's ends.
In New Jedi Order and beyond there has been a lot of experimentation with techniques that would have been banned under the Jedi Council.
The current Jedi Order seems to have taken an approach akin to the Shao-Lin seeking Discipline and Control over Emotion, allowing for slips and mistakes and having the belief that the fallen can be redeemed if brought back early enough. It is not uncommon to see the different Jedi straying towards the dark side (including Leia) only to be brought back by the masters.
Drawing a line between the light and dark side is a very subjective decision.
For example, we know that Mace Windu used a fighting technique he called Vaapad, which channeled raw ferocity from the opponent back at them. This is described as stepping over the line into tapping into the dark side of the force, but is an acceptable Jedi technique (although dangerous).
So light versus dark is really a personal if not organizational designation determined by subjective ethics.
The Force is ambiguous (do Midichlorians really pick sides?). It is the desire of the person using the Force that can be considered "Light" or "Dark". The reason why some powers are associated with Sith (or Dark) vs Jedi (or Light) is likely because some are easier to enact using one method over another (raw emotion versus mental discipline).
A gun is neither good nor evil, nor is any 'thing' (and with this I would include a "power" as a thing). It is all about HOW it is used and perhaps more importantly WHY it is used. Several examples have been provided already about how a power can be used for good or evil, I would challenge anyone to suggest a power of the Force that could NOT be used "for good".
Leaving us with "the difference" being in the heart or mind of the person using the Force, and in 'the Force' itself.
In my opinion, the dark side represents death, and the light side represents life. I think in one interview Geoge Lucas said that the sith are evil not the dark side
I hate bring feminism down on the crew here, but the overwhelming gist of the Force seems to me to be very Old Testament. I mean, where are the chicks in positions of power? Princess Leia never gets to fly in battle, and Padme just wrecks everything. Oh, yeah, and she dies in childbirth yawn.
I guess the force is just to keep me in my place. There's some hope though. Since the rights of black men generally precede the rights of women, there is a Black man jedi.
A. The dark side gets laid.
The difference between the light and the dark side of the force is life itself. The force may appear neutral but since the dark side is usually used to kill or do harm to other beings while the light side respects and protects life as much as possible, then those who used the light side in the long run will probably be in a stronger and better position to triumph because of the more numerous allies they are able to make and instruct, over time compared to the Sith Lords who only live to dominate and do harm to others, Sith included. They are always fighting each other for survival or power. Why do you think the Jedi are able to establish an order and high council while the Sith regularly stepped on one another and have to abide by the famous "rule of two" of Darth Banes?
That means, while a Jedi, no matter how strong he can become is no threat to another one, and are allowed to freely multiply themselves by the thousands and become a very strong force, the Sith can only be allowed to be two of them at the same time: One Sith lord and his apprentice. Thus, no matter how strong the dark side, on any given day, a dark lord, no matter how powerful will have to confront thousands of Jedi at the same time. Then, because of their strength in numbers, the Jedi can only be defeated by the Sith lords only through extraordinary means of treachery, surprise or treason. The servant of the light side would win 9 battles out of ten. Ultimately, eventhough the dark side of the force may appear more appealing and more powerfull on a personal point of view, it is nonetheless self destructive and doomed to be defeated by too many enemies(the Jedi).
To understand my answer you must understand what the Star Wars Galaxy truly is.
The Star Wars galaxy at its core is a galaxy governed, ruled, and enslaved by an extremely active, omnipresent, and malevolent Fate - both Light and Dark are the intrinsically flawed creations...of Fate itself.
The Force/Destiny/Fate creates a light side and a dark side picks its champions for both sides and pits them against one another with everyone else in the galaxy - all those normal men, women, and children born without Destiny's yoke pressing down on their souls - getting caught in the crossfire.
I will start by shocking you. The Light Side has a very clear, very deep, very persistent hypocrisy to it. Yes, it claims to value personal 'life' and personal 'freedom' but it subordinates both to 'listening to the Will of the force' and fulfilling the purpose of Destiny - an external force that lesser beings are told to trust and worship without question.
Fate is a collectivist argument that promotes servitude to the rule of Destiny's chosen champions - the light side or the Jedi. It creates and channels a dependence on the Jedi to solve their problems giving rise to indolence, corruption, and moral decay...setting the stage for the Dark Side to rise again. Destiny wants only its champions to have intrinsic worth since those are the people it directly controls...everyone else is its meat and drink...its bloody spectacle...its entertainment...
In other words, the Jedi are the ones Fate acts through directly and it uses them to reinforce its grip on the rest of humanity. No Jedi ever earns their high place in the galaxy. Destiny makes its picks, fills those champions up with free power, and charts their actions from cradle to grave making their arrogance, pride, angst, and whining all the more infuriating, childish, and insultingly stupid to those born outside the loins of the chosen few royalist families Destiny loves to play with...
Bottom Line, thee Jedi do not earn their power through merit or personal achievement but from 'royal birth' into the right families or the puckish whims of a galaxy spanning Fate that plays mortals like puppets for the sake of its own amusement. Think of Light Side as Destiny's favored side in a very bloody game of football and the Dark side as everybody that may oppose Fate's control over them. Fearing the Dark Side, Fate stacks the deck by supplying the dark side with force-sensitives who are twisted into corrupt mockeries of themselves that don't hesitate to grind them up with the end result of all Sith philosophies.
All Force-sensitives are enslaved by Destiny's yoke on their soul from birth and gain Fate's incredible superhero powers to act in its interests. Dark side force-sensitives are Fate's way of culling all those who value personal liberty and personal merit and personal value from the galactic population pool of souls while simultaneously discrediting an individualistic value system and worldview that threatens its stranglehold over creation and its very existence.
So yes, Fate uses the light side as a proxy for its own side (and point of view). Destiny twists the other side the Dark Side into a hateful mockery of its own ideals so that a Destiny centric position is "proven" correct as a result of whatever its most recent force-sensitive controlled war of annihilation and conversion happened to be.
Its viewpoints are reinforced among normal human beings (who as a rule don't want to die) along with every other non-force wielding sentient while culling the herd of the rest.
The truest ideal of the Dark Side is to overcome Fate in the hopes of creating a utopia where Fate falls to the personal liberty of the individual who earns his or her successes in life instead of having those successes handed to him or her by Fate...Fate deliberately warped this ideal by twisting some of the children whose yoke of Destiny is stronger than any other into malevolent mockeries of this ideal. This is shown by those force sensitives who are the worst sort of death seeking blood knighted power hungry tyrants who routinely try to crush the liberty and personal value of those 'beneath them' until it utterly takes their lives allowing Destiny to collect their souls and torture them.
Thus the deepest truth in Star Wars is that most of humanity and every other sentient is mere grist for the mill of the bloody whetstone of Destiny...any personal accomplishment or determination is rendered meaningless by those Fated to succeed over them...and an individualistic point of view is discredited by the Destiny's dark-sided children.
In summary, all wars in Star Wars are tools of Fate to preserve itself from all those who have Free Will. The Light side and Dark side are false artificial sides controlled by Destiny so that Fate may reinforce its Will and trample on the will of the vast multitudes who exist outside its direct control using a relative handful of people that it can control directly to serve its interests as well as provide it with its chosen form of entertainment.
