http://www.beingjewish.com/basics/satan.html(This article should be read after my article Why Did G-d Create the World?)
The Christians don't understand how an angel of G-d can try to seduce people to disobey G-d, so they came to the unsupported conclusion that Satan must have rebelled against G-d.
This is completely contrary to everything Judaism believes. We reject that interpretation entirely.
What, then, does Judaism teach about Satan?
Did you ever see the movie Willy Wonka and the Chocolate Factory? (It's one of the few examples of where a story from a book was changed for the screen without ruining the experience.) The story is about a very famous chocolate factory, called Willy Wonka's Chocolate Factory, that produces the world's greatest chocolates, candies -- confectionery in general. No one ever enters the factory, and no one ever leaves.
Mr. Wonka, the owner, runs a contest. The winners of the contest will be allowed to enter and tour the factory together. However, they will have to sign a contract and follow the rules. One of the rules is: no eating of any products inside the factory without express permission.
Afterwards, when they leave, they will go home with a lifetime supply of chocolate.That is, *IF* they follow the rules.
Five children win. They are of course all excited; TV stations and reporters interview them, and the whole world is excited with them. Now they just wait until the day they are to enter the factory and see the great wonders that no one else has ever been allowed to see.
Before the big day comes, each of the winners of the contest is secretly visited by a man named Arthur Slugworth, President of Slugworth Chocolates, Incorporated. Mr. Slugworth shows them a lot of cash, and tells them they will get all that money and more, if only they steal out of the factory a candy called an Everlasting Gobstopper. See, it hasn't been mass produced or marketed yet, and Wonka's competition wants to get an advance sample of this product so he can get it out first, and ruin Wonka.
The day comes, and all the kids are allowed into the factory with one adult relative. They see the most amazing sights, and eat the most amazing (and impossible to actually exist in real life) foods. One of the things Wonka gives each of the kids is an Everlasting Gobstopper, on the condition that they never show it to anyone else.
During the tour of the factory, four of the kids break the rules by taking stuff they should not have taken, and they all suffer the consequences. One gets all swollen up and blue from some gum she should not have taken, and they have to take her away and squeeze her until she gets skinny again. One of the kids jumps into a pool of chocolate and is sucked up into the pipes. And so on. They are all saved in the end, so don't worry, but they must leave the factory without the lifetime supply of chocolate, because they broke the rules.
Charlie, the main character, also breaks the rules. He drinks some Fizzy drink he was not supposed to take, but no one seems to know, so he doesn't say anything. He doesn't get hurt in the process, so he survives until the end of the tour.
At the end of the tour, Charlie Bucket and his grandfather are the only ones left. Mr. Wonka says good bye to them, and tells them to leave. Upset, Charlie asks him for the lifetime supply of chocolate. But Mr. Wonka has somehow found out that Charlie drank the Fizzy drink, and therefore broke the rules. Charlie will not be getting a lifetime supply of chocolate either.
Wonka yells at him for drinking the Fuzzy drink, and Charlie feels bad. But his grandfather is angry, and he tells Charlie that they'll give Mr. Slugworth an Everlasting Gobstopper.
They are about to leave, when Charlie realizes that no matter how he feels, stealing and breaking rules is bad. So he goes to Mr. Wonka's desk and returns the Gobstopper to him.
Wonka sees that, and jumps up in delight! He tells Charlie that he has won! Charlie has no idea of what he's talking about. It seems that Wonka was looking to retire, and so he set up the contest to find an honest child he could train as his successor.
Then Wonka calls in Wilkinson, his aide. And Wilkinson is Slugworth! Slugworth was sent out to each of the children to test them! To see how they would respond. Anyone who either ate food he wasn't supposed to eat or brought a Gobstopper to Slugworth was dishonest, and would not become the successor. (Okay, the parable is not exact, but I think you get my point.) Notice, also, that Wonka himself gave each of the children a Gobstopper. So he himself set up the choice, and then gave them the opportunity to break the rule, using Wilkinsin to offer the temptation.
Christians take Slugworth at face value: a reprehensible competitor who will stop at nothing to undo Wonka. And that's how they view Satan.
Jews do not see it that way, and we never have. Just as Slugworth is really Wilkinson doing what Wonka asked him to do, Satan is also not working for himself.
The Hebrew word "Satan" means "Hinderer." To hinder someone means to hold him back, to try to prevent him from doing something. G-d created the Hinderer to give us work to do in this world (see my article Why did G-d Create the World?). Satan is here to make things difficult for us, so we can overcome our evil temptations, and PASS the test. That is the purpose of Satan. Satan is an angel whose purpose has been determined by G-d.
Temptation is there to try and deter us. It gives us the ability to do the wrong thing. More importantly, it gives us the ability to look at evil and refuse to do it. By presenting us with the opportunity to do evil, it gives us the ability to choose between good and evil.