Explanation of Jules' ending monologue

This question has already an accepted answer, but I feel the need to answer anyway, because I have a very different point of view. I'll use the same breakdown that phwd uses.

See now I'm thinkin', maybe it means you're the evil man. And I'm the righteous man. And Mr. 9 Milimeter here, he's the shepherd protecting my righteous ass in the valley of darkness.

The simplistic and egotistical version. Ringo is trying to harm him, and can be classified as simply bad. Jules is free to do whatever he wants.

Or it could mean you're the righteous man and I'm the shepherd and it's the world that's evil and selfish. Now, I'd like that. But that shit ain't the truth.

Assume that Ringo is a good man, and is forced to his path out of pure desperation in an unjust world. Jules can protect and guide him, as he knows much of the world. As Jules said, he would like that. Jules would like to believe that he is a good person, and could help others with his new-found spirituality.

The truth is you're the weak. And I'm the tyranny of evil men. But I'm trying. I'm trying real hard to be the shepard.

Jules recognizes that Ringo isn't a truly bad person at the core: he doesn't want to hurt people (as mentioned in Ringo's speech), he loves his girlfriend, etc. He is weak, and takes the easy way out by robbing people, but doesn't want to actually hurt people. But that's not the life that Jules has led. He hasn't tried to avoid hurting people...he has killed many people and thought nothing of it. Jules has come to realize that he has led the truly evil life. But he wants to change. He knows it won't be as easy as just saying it. ("Now, I'd like that. But that shit ain't the truth.") He has to live it. And he starts by showing compassion, restraint, and mercy by not only letting Ringo live, but by letting him keep the money...giving him a lesson not of strength, but of generosity.

There are three explanations.

See now I'm thinkin', maybe it means you're the evil man. And I'm the righteous man. And Mr. 9 Milimeter here, he's the shepherd protecting my righteous ass in the valley of darkness.

The kid is led astray, Jules is on right path and his gun (and the idea of being killed) is the item preventing him from going off his path.

Or it could mean you're the righteous man and I'm the shepherd and it's the world that's evil and selfish.

The kid didn't do anything wrong and it Jules' boss and to an extent the system of drugs and money that is evil and selfish. But why would Jules be in the room in first place if the kid didn't do anything wrong. Jules wants that. Jules want to lead everyone to path of righteousness. He doesn't necessarily want to kill him. But it is his job.

The truth is you're the weak. And I'm the tyranny of evil men.

This makes the most sense. Jules is the oppressive power of his boss and the kid without the firepower or money is the weak.

In summary, Jules instead of killing him on the spot remarks at the significance of choice within the valley of darkness (the world) to be the shepherd, the righteous or the evil man. And in some cases, the evil man comes out on top.

Simply: up until now Jules has been evil - now he's gonna try to do right, which is harder. You have to remember that this quote comes in the context of Jules quitting the business.