In light of the fantastically choreographed climactic lightsabre battle of 1999's The Phantom Menace the duels fought by next-generation hero Luke Skywalker seem a little slow, a little clumsy and a little forced. In light of the calm poise shown by Qui-gon Jinn and Obi-wan Kenobi during times of tension and trouble, the junior Skywalker's nearly complete inability to control his adolescent emotional outbursts stands in stark contrast to our amplified notion of how a Jedi Knight might comport himself.
The Jedi of the Old Republic as seen in The Phantom Menace and glimpsed in the promotional material for Attack of the Clones are clearly of a meditative ilk, demonstrating their lightning reflexes and deadly fighting techniques only when pressed. When they are pressed, they dispatch their enemies with a slick efficiency never dreamed of by the likes of Luke and his "take me seriously or else" posturing.
A question naturally arises in the minds of thoughtful observers of the saga: how can the elaborate tapestry of fate and personal destinies woven by the Force be consistent with Luke being such a retard?
It is my proposition for your consideration that Luke's failings as a Jedi are not only permissible by the fate that the Force engineers, but in fact completely necessary to ensure the successful realisation of that fate. In other words, if Luke were less of a gimp, the Empire would not have fallen and the New Republic would never have come to be.
This conclusion is based on the premise that the crux of the Force's manipulations comes at the moment when Darth Vader looks on as Emperor Palpatine is blasting the bleating and incapacitated Luke Skywalker with bolts of evil energy. It is at this moment that the persona of Anakin Skywalker reasserts itself from within Vader, wrests the Emperor away from Luke and throws him down a long (and apparently fatal) shaft. Presumably, if Vader had not been moved to intervene, Luke would have been killed and, somehow (see footnote), the Rebel Alliance would have suffered as a result of this.
Why does Anakin act? What motivates him to do that which no argument can, to reassert his non-evil persona? What breaks through the darth veneer of Vader, and reveals the deeply wounded human being underneath? What, in short, melts Anakin's frozen heart? It is pity.
This single moment of pathos is the fulcrum upon which pivots the two possible fates of the galaxy, Empire or Republic. The lives of trillions rest in the faith that one man will be touched by the tortured cries of his dying son. It is a moment that the force has deliberately shaped Anakin and Luke for, built them from the ground-up with this final confrontation as the most important moment in both of their lives. By design, Anakin has become Darth Vader to fulfill his half of the confrontation; thus, by design Luke has to become an earnest but ineffectual failure to fulfill his.
Consider: if Luke were in control of his emotions like a true Jedi Knight, he would have executed Darth Vader when he had the chance, as Luke stood over his fallen foe -- much as Obi-wan Kenobi had executed Darth Maul without hesitation, years earlier. Instead, Luke mutilates Vader to avenge his own mutilation, by cutting off his father's right hand. If Luke had killed Vader, no one would remain to save Luke from Palpatine. Luke's adolescent rage and desire for vengeance assures that Vader will not be killed in one swift stroke.
Consider also: Luke refuses to "strike down" Palpatine after noting the poetic symmetry between the severed hand of his demi-robotic dad and his own robotic limb. If this refusal is as significant as Palpatine would have us believe, then it is of the utmost consequence that Luke is originally wounded by Vader in the climax of The Empire Strikes Back. Once again, one of the symbols that would attain great significance in the Force's great moment of decision is acquired through Luke's lack of swordsmanship, as he leaves himself glaringly open to Vader's attack.
While the inner workings of the fulfillment of the prophecy of "the son of the suns" and the Force's motives (for lack of a better term) for creating Anakin might remain a mystery, it is clear that the role of Luke Skywalker is to present a pathetic enough image to move Anakin to resurface, using the power of Vader to destroy Palpatine, and with him the Empire. Luke's self-inflating pretensions and childish rage ensures the appropriate emotional response, and his impatience and failure to grasp the basics of the Jedi fighting philosophy ensure the appropriate physical response. Luke's foolhardy posturing and poor lightsabre skills set him up for his moment of personal destiny, when everything that he is is called upon to whine and squirm while being slowly roasted by Palpatine.
Luke delivers, Anakin is moved, Palpatine dies, the ewoks dance, the computer-generated people vandalise Palpatine's statue on Coruscant, and the galaxy awaits the birth of the New Republic. And none of it would have been possible if Luke hadn't been such a pitiable goof.
I thank you for your attention / je vous remercie pour votre attention.
It can be argued that Luke's show-down with Palpatine is entirely inconsequential, on the grounds that Palpatine and Vader would be killed just a few minutes later when the Death Star explodes. Han Solo's successful destruction of the Imperial shield generator on Endor did not rely on the outcome of the duel. There is no obvious reason to think that the rebels would fail just because Luke had been killed, but we choose to suspend our disbelief rather than admit that the plot of Return of the Jedi is riddled with several major irreconcilable logical flaws. But hey -- it's Lucas, not Shakespeare.