In Episode 5, Luke goes to Dagobah where he is told he is too old to be taught in the ways of the force and then it is later stated by Obi-Wan that he was their last hope. If he was their last hope why wasn't he taught about the force from an earlier age? Least then he would have been a lot better prepared and probably could done a lot better against Vader, but lets face it...he beat Vader cause he felt anger that Vader wanted to turn Leia to the dark side.
From Episode III on to Episode VI, there wasn't a safe environment to train Jedi in; the Empire was looking for them everywhere. When Yoda & Obi Wan went into hiding, they might have pinned their hopes of eventually rallying some surviving Jedi they could find. But the Empire kept the hunt going for twenty years, which is why Obi Wan can tell Luke with some definitiveness that the Jedi were all but extinct.
They likely sensed the great force potential in both Luke & Leia as infants, but then wasn't the time to deal with it. Obi Wan said he would watch over Luke from afar on Tatooine and decide what to do when the time was right. The secret resistance started by Bail Organa in Episode III knew he was there and likely kept in some contact, seeing as Leia eventually went to get him for the Death Star mission. So yes, there were taking a risk by starting Luke's training late, but fate had dealt them this hand and they risked it.
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"I'm not smart so much as I am not dumb." - Harlan Ellison
Well how come they weren't training leia as well then at the time they were training Luke? Why not train them both at the same time? I'm guessing they thought by that time the emperor knew of Luke and not leia as a potential jedi?
Well if the Jedi knew everything and couldn't possibly be wrong about how they did things, they wouldn't have made mistakes that led to their downfall and have been better prepared for the rise of the Sith. That's part of what the PT showed; they had become a static, rigid organization that needed more radical thinkers like Qui-Gon Jinn, who would have been on the council if not for the perception of him as a rebel & maverick. Anakin would likely had never fallen to the dark side if he had lived to train him.
And if you read the novelization of the Revenge Of The Sith, Yoda has an inner monologue while fighting Palpatine, when he realizes the Sith had changed while the Jedi had not; that is why they wouldn't be victorious now.
So all of their pre-conceived rules about how-to-do-things-in-the-order hadn't prevented their fall from power. So they went a different route with Luke & Leia. I'm sure some of this territory will be covered in the live action series to come.
Do you think it's possible Obi Wan was sleep-teaching Luke in his subconscious, between ANH and TESB? Three years had passed, and now Luke can use the force to pull his lightsaber to him. So I think Obi Wan in his force ghost form was doing as much as possible, before he considered it time for Yoda to take over. Again, radical change from the previous years in the Jedi, because Yoda only taught the younglings before they were paired off with a master. Now it was inverted, with him finishing off an adult Luke.
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"I'm not smart so much as I am not dumb." - Harlan Ellison
I did read the ROTS, but of course the OT didn't take into consideration of the PT showing that the jedi was as you say a static, rigid organization that needed more radical thinkers.
Obi Wan could have easily shown Luke the ways of the force before ANH, it's not like Vader felt Luke's presence on Tatooine when he was hovering over them...or even on the death star. Luke probably would have beaten Vader in ESB but we can never be too sure of that. In ESB he showed some good skills and believe his sabre should've taken Vaders arm off but thats a different point entirely.
I dunno if teaching him earlier on would have made it easier for the sith to find him.
They didn't tell him because they wanted Vader dead, plus look at ROTJ...after Luke knew he didn't want to fight Vader, so they lied to him so that Luke wouldn't hold back when facing Vader
Luke was about to fall the dark side? I dunno about that, he managed to resist temptation from the dark side...the emperor and his dad both tried and failed...how do I know they failed? Because the emperor decided to kill him. If he'd been trained sooner maybe he would've known a lightsabre could protect him from force lightning.
Anakin was closer to the dark side than Luke ever was...but Yoda still let Obi-Wan train him sooner than Luke was trained.
When Yoda said that, that was before Vader/Emperor approached him... It was clear both sides were going for him. " The Emperor knew, as we did, that if Anakin were to have any offspring, they would be a threat for him."
And as we know Anakin had offspring, twins. Luke could have easily been trained from an early age considering he was meant to be a threat to the emperor.
Maybe training him would have sent tremors in the Force and alerted the Empire to new Jedi. I always thought Jedi were at least sensitie to each other. I'd had hoped to see more of Anakin while he 'helped hunt down and destroy the Jedi knights'. He didn't do much hunting down as far as we saw, only kill kiddies... But that's beside the point.