The claim that God does not exist is a positive assertion of a negative claim. When it comes to the claim that God does not exist I don't see how it is my responsibility to prove that he doesn't even though I make the claim based on lack of evidence and my personal experience. Why is it that theists insist that we try to prove a negative? I am of the opinion that you can't prove that God exist or doesn't. As the religion states it's one of those things that you just have to accept in faith.
The claim that God exist is unprovable for many reasons of which I will outline a couple of the most common ones in this post. The first and biggest problem with proving the existence of God is that he or it is invisible! The fact that he is invisible makes it impossible to prove by seeing him because he is of an immaterial nature. Not only that but if you happen to see him you will die! I am aware of some contradictory texts that state that Moses saw God face to face etc. but for the sake of argument just play along.
20But,” he said, “you cannot see my face, for no one may see me and live.” Exodus 33:20
I find this problem most troubling and quite convenient for the believer. This is one of those cases where absence of evidence is evidence of absence. You can't see God but you must believe that he exist. Your only basis for belief is faith which in all truth nothing but blindly accepting something without evidence. Faith is truly blind and it requires nothing more than belief to make whatever you can imagine a reality.
And without faith it is impossible to please God, because anyone who comes to him must believe that he exists and that he rewards those who earnestly seek him. Hebrews 11:6
Another problem with proving the existence of God is that he exist in a realm outside of our known space and understanding of time. Once again this is quite convenient for the believer. Because of this it is impossible to test the theory that God exists without him voluntarily making himself known and available. But of course doing so would defeat the necessity for believing in God through faith alone. According to Christian teachings God wants you to know and serve him but he doesn't want to make himself known.
Another problem is the problem of miracles. We hear about them all the time and believers assure us that they are acts of God. But I have personally never seen a real miracle in the sense that God intervenes in the laws of nature in such a way as to make something that is known to be impossible to occur. For instance it would be quite a miracle if God healed amputees. The Bible mentions miracles of God such as healing the blind, death, mute, and even paralytics but you never read about him restoring a limb. Humans are unable to regenerate limbs that have been torn off or medically amputated. In this regard the following link has some good questions about the existence of God and its relevance to amputees.
It's funny that all of the rigorous requirements that theists try to put on us nonbelievers only apply to the existence of God. Reason and logical thinking does not apply to God by default and therefore they don't seem to see the hypocrisy of their position. We don't believe in Santa or in elves but we don't go out to the North Pole to try and find him either. In all reality God can't be found because he exists only in the imagination. I find the idea of God utterly ridiculous and completely irrational.
There are so many things in this world that make sense from a naturalistic point of view without requiring the existence of God or demons, devils, and angels. Natural disasters, children dying violent deaths, women dying while giving birth, etc. all these things make sense without inserting a personal deity into the picture. Not all events of our lives have to have a reason not everything ends with a why behind it. When you put God into the mix all you do is create for yourself a mess of unnecessary and irrational questions that just can't be answered.
The Christians famous "God works in mysterious ways" doesn't work in the real world. Or blaming certain tragedies on Satan or someone being possessed by a demon makes absolutely no sense at all. A mom who murderes her own child or a child who kills his parents cannot be logically explained since we don't know what was going through the perpetrators mind at the time. But saying he was possessed by Satan just makes a bad situation seem worse and creates a bunch of stupid and nonsensical why questions.
God doesn't explain why evil exists nor does the biblical explanation for the existence of evil since it basically tells us that it came into existence when mans innocence was shattered after the fictional Adam and Eve ate the forbidden fruit. It is because of this one act of disobedience to God's command that mankind has inherited sin as if it were some form of a genetic trait. The Bible wants you to believe that you are born with a debt to this God and it is only payable by accepting Jesus as your Lord and savior. Submitting your life to him and believing that it will put you back in God's good graces.
Having made my case in this post I think that atheism is the logical position to take when it comes to the existence of God. Agnosticism on the other hand in my opinion makes no sense because you are assuming that God could exist but that we can't know for sure since we don't have enough information to make that call. How much information do you need? There is zero evidence of the existence of God and because of the fact that he is outside the reach of scientific discovery I dare say with confidence that there is no God and that there never will be evidence of his existence. God is the creation of mans imagination and nothing more.
Note: All biblical citations are taken from the New Internation Version