Jacob explains that the island is a cork to contain evil, gives Richard eternal life

Richard sits outside the statue wrapped in a blanket as Jacob approaches carrying a bottle of wine. Richard asks what is inside the statue and Jacob only says that no one comes in unless he invites them in. Jacob tells Richard that he is not the devil and reveals that he brought the Black Rock to the island.

Jacob then tells Richard to think of the wine in the bottle as hell or malevolence, evil or darkness. He says that if the evil got out, it would spread and that the cork in the bottle is the island, which keeps the evil where it belongs.

He continues explaining that the man in black believes that everyone is corruptible because it is in their nature to sin. Jacob says he brings people here to the island prove him wrong, because on the island, their past doesn't matter.

He said that before Richard, there were many other people who all died. Jacob says that he didn't help the people because he wanted them to help themselves and to make the decision between right and wrong for themselves. When Richard points out that if Jacob doesn't step in, the man in black will, this intrigues Jacob, who then offers Richard a job as his intermediary. Richard would be the the one to interact with the people Jacob brings to the island.

Richard asks what he'll get in return for doing the job. He first asks for Isabella back and Jacob says he can't do that. Then Richard asks for his sins to be absolved so he won't go to hell, but Jacob says the can't do that either. Finally, Richard says that he never wants to die, he wants to live forever. Jacob says he can do that, and touches Richard on the shoulder.

So this scene was possibly the biggest mythological reveal to date. We get an explanation of the island's possible purpose from someone who would actually know. The question is, what happens when the cork is not in the bottle and the evil escapes? What consequences would there be? And how does the island act as said cork? What force is it that keeps the evil on the island?

We also see the moment where Richard became the ageless go-between we've come to know. It's surprising that he asked to live forever rather than Jacob giving him the gift on his own.