The Purpose of Satan

This is something that God taught me while reading Revelation. First, here's the passage:

"7Now war arose in heaven, Michael and his angels fighting against the dragon. And the dragon and his angels fought back, 8but he was defeated, and there was no longer any place for them in heaven. 9And the great dragon was thrown down, that ancient serpent, who is called the devil and Satan, the deceiver of the whole world— he was thrown down to the earth, and his angels were thrown down with him. 10And I heard a loud voice in heaven, saying, "Now the salvation and the power and the kingdom of our God and the authority of his Christ have come, for the accuser of our brothers has been thrown down, who accuses them day and night before our God. 11And they have conquered him by the blood of the Lamb and by the word of their testimony, for they loved not their lives even unto death." (Revelation 12, ESV)

Well, this is a cool passage because it gives us the background info on Satan. In Genesis, we don't know exactly how he came about, except that he tempted Eve, which therefore led to the fall of man. But, I've always kind of wondered, why do we even have Satan? Wouldn't things be much simpler if he weren't here at all? Think about it, no sin, no death, eternal life for all. But then, as I was reading, I got to verse 10, and I was like, wowwwwwww. Did you catch it, did you have the wow moment? Read it again. Again, until it makes sense. It's all about the sovereignty of God. If Satan had not been cast out of heaven, there would indeed be no sin, at least not through him anyway. No sin, so no need for salvation, no need for a Savior, no need of Christ. It is because of Satan, because of sin that the God who created the universe and us came to this earth to live among us, to die for us out of love and obedience, so that we could have righteousness and eternal life through faith in him.

But then, you still get back to the question, why have sin though? And then I realized, it all boils down to love, to choice. What does love and choice have to do with each other? Everything! God could have easily created sin-proof robots that would never sin against him. But, that takes the choice out of it, and there is no love if there is no freedom of choice. God gave us the gift of choice so that we could choose to love him, he doesn't force us to love him. That is true love, that we choose to love him. And thus, we have the choice to sin, the choice to love, the choice to be his child. And so, to bring sin into the world, and therefore choice, we had to have that "serpent of old, called the Devil and Satan (NKJV)," which thus resultingly paved the way for Christ, for salvation, and for the kingdom of God.

The sovereignty of God is so incredible, it really blows my mind!