Do you believe in the existence of the Devil?

I believe in God. Therefore, I also believe in satan. Where there is good there is also evil. Where there is evil there is also good. You can't have one without the other. Because if you did, how would you know the other? In order to know what good is you must also know what evil is. And vice versa. We wouldn't know what light was, if we didn't also know what darkness is. It just makes sense. It is logical. Even if you took God and religions out of the equation. It still makes sense. "That they may know from the rising of the sun, and from the west, that there is none beside Me, I am the LORD, and there is none else. I form the light, and create darkness; I make peace, AND CREATE EVIL: I the LORD do ALL THESE THINGS" (Isaiah 45:6-7) God created satan in order for humans to know the difference from good and evil.

No, I don't. Why? I haven't seen the Devil, just like I haven't seen God. The devil is part of the Catholic and Christian. I don't belong to any religion. To me the devil is a myth. Something invented by men to scare people off and nothing more.