Every time you doubt, something I have never done, BTW, pick up a grass straw or a leaf, could we make one by our own knowledge? No. So it is a very logical conclusion to say that God do exist. And if we believe in God we must believe in Satan. But it is very important to understand that we shall not WORSHIP Satan. He do exist, as the evil force, but God are the good and loving force and will win in the end. And how do we know God will win? Love and understanding is always stronger then evil ever can be.
If both good and bad would be a myth or just a good story we would know it by now. There are all evidence that say: God is real. Science can not explain God, but everything do not need a scientific explanation. Some may ask “what evidence” and for a good reason. I do understand that it can be hard to have faith sometimes and even impossible some other times. So what evidence? Do you think a lie would last for 2000 years? People was not stupid then, they saw with their own eyes what Christ did do. They saw that He did die, and keep in mind that those who did witness that where not what we today call Christians. Why would they lie? Behind every lie is a need or goal to not tell the truth. They did not gain anything. If the only people who would have seen Christ die had been his disciples we would have a problem with what really did happen, but those who did see it where Roman soldiers who had no interest to tell “a good story”. And what make the truth even more true is what did happen after the Crucifixion. If it all would have been a lie we would most likely have only The Old Testament and a Jewish faith. But truth will ALWAYS win. It was not a well staged “show”, it was the truth.
Many say that The Bible is “full” of contradictions. And sure, there are a few, but anyone who read The Bible more then once will understand that what may be a “contradiction” is only a small error in translating The Bible. Furthermore, there are NO contradictions in The New Testament. Four Gospels tell the same story, almost word to word. But this is not enough for some people, but there is more. If someone would argue that The Bible and above all The Gospels are fiction there is too many historical events to back up The Gospels. When all these factors are glued together there is all evidence we need. For every “ah, that can’t be true, I don’t believe you” there is two or more passages that will overthrow arguments against The Truth. And you see my friend, what I do right now, writing this answer is the last and most reliable evidence in the whole chain. Me and all others who right now, at this very moment are spreading The Gospels are the evidence. Do you think that I am so stupid and so childish that I would be lying to people about this? Why would I do it? What would I gain? Nothing, absolutely nothing what so ever.
The truth my friend, is what it is, namely the TRUTH. So go back and read The Bible, and if you can, compare it with history-books, maps of Israel as it was 2000 years ago, and you will come, eventually, or right a way to the final conclusion, it must be true. I hope you will find what you look for, and be aware of Satan, He is clever, and smarter then we often think, but Satan who is the night, the very darkness, will face the daylight, and fall as all evil in this world will so have faith also in what you can’t see or argue either way. Faith is to believe in the truth, and God is as true now as He was in the beginning of time.