Originally posted by Ushgarak
We can be fairly sure that most Jedi are accepted in infancy; Quo-Gon says that they are detected quickly, after all.A point- Luke is NOT that well trained; he is extraordinarily talented and has great potential, but by the end of ROTJ he is no more talented than a Padawan, if that.
He beat Vader a. because he unleashed his enormous potential in the form of anger b. his father was in conflict about fighting him and c. Vader was not as good as he was; his injuries had slowed him considerably.
It was also dramatically appropriate...
He lacks combat experience yes, but the Force is with him far more powerfully than that of a mere Padawn. A Padawan would not have been able to survive the lightning of Palpatine, nor defeat Jabba and his entourage practically single-handedly.
As to Vader, Lucas said in an interview that Vader's injuries not only took his organic limbs, but robbed him of most of his Force potential. As Vader, he possesses roughly 80% of the Emperor's power, (still making him far more powerful than even Yoda) yet had he suffered none of his injuries on Mustafar he would've been twice as powerful as Palpatine.
The suit Vader wears is extremely heavy and all of his limbs are robotic, which accounts for his apparently significant physical strength as well as his complete lack of agility in OT duels.
Luke become a Jedi after defeating Vader. Whether he could have taken the Emperor or not is not the issue; had he done so, he would've likely turned to the darkside as Palpatine would've no doubt played the defenseless old man card again. This is why Luke had to throw his lightsaber away and leave himself open to the Emperor's lightning.