Locke takes Ben to the temple, Ben is sorry to what he did to Desmond

Back in the jungle, as Sun, Ben and Locke are walking towards the temple, Ben asks Locke "How is it you know where you're going?" Locke says "I just know." Ben asks "And how does that work exactly, the knowing, I mean did it come upon you gradually or did you wake up one morning suddenly understanding the mysteries of the universe." Locke asks him "You don't like this very much, do you? Having to asks questions that you don't know the answer to, blindly following someone in hopes that they'll lead you to whatever it is you're looking for." Ben says he doesn't like it at all. Locke replies "Well, now you know what is was like to be me." Sun jumps in and tells them that they should keep moving.

As they start walking again, Ben says that he thinks he knows where they're going. It's the same place they brought him as a child, where the island healed him. Locke says as they arrive at the temple, "I hope it's as generous this time around." Ben says that this is actually the wall around their temple. Ben says the temple is actually about a half mile from here and the wall was built to keep people like Sun and Locke from every seeing it. Locke tells Ben that they're not going into the temple, they're going under it. This causes Ben to have that freaked out, panicked look on his face. It a moment of seeming sincerity, Ben asks Sun to do a favor for him. He asks her to find Desmond Hume is she ever gets off the island and to tell him he's sorry. Sun asks "Sorry for what?" and Ben replies "He'll know." Ben slowly steps down in the hole which appears to be the same on the French team went in to try and save Montand.

So the question still remains, how does Locke know what he knows now? How did he know to go to the temple wall and go under it? Also, Ben's sincere apology he wants delivered to Desmond is quite moving. Ben obviously didn't think he would come out of the from the temple alive.