The difference between not believing in God, and believing He doesn't exist

One of the harder concepts to grasp about atheism, particularly for Christians or others who fail to comprehend what atheists 'believe' in, or believe doesn't exist to be more specific, is the notion that, instead of believing God doesn't exist, we atheists don't believe in God. Now I can practically swear that 99% of you who read that last sentence would probably say that those two notions are essentially the same damn thing, no? Wrong.

This is a very tricky concept to understand; I myself had to grapple with it for a while before it finally became clear through my thick skull (but then I do have Asperger's after all, meaning it's harder for me, to a point, to comprehend abstract ideas and notions). The best way I can think of explaining it, is visually – hence the quick graphic I made below.

The above pic is a scale of sorts, a horizontal line that measures the varying strengths of people's beliefs or disbeliefs of God. The further you are to the right, the more you believe in God; the further you are to the left, the less you believe in God, more you believe He actually doesn't exist.

There are three basic groups of people when it comes to beliefs in deities such as God: Theists, Atheists/Agnostics (the latter absent here to save space), and Antitheists.

Theists are those who do believe in God, and generally support him – Christians, Muslims, Mormons, and etc.

Atheists are those who neither believe He does exist, nor believe He does not exist. They simply don't believe He exists – ie., they aren't on the right of the scale, but aren't on the left side, either.

Antitheists are those who actually believe God does not exist and would vouch for this. In this sense, many atheists would actually be labeled or classified as antitheists, as not only do they not hold the belief in His existence, but they actually believe in the exact opposite, in His inexistence.

However, I, along with most atheists, I think I can safely say, are neither to the left nor the right of my little scale above. We do not believe in him not existing; we simply do not believe he does exist, either.

I hope this makes it a little more clear, if anything, as to what it means not to believe in something, rather than believe in it not existing. That's my personal stance on the matter: I cannot presume to state, with confidence or knowledge, that God doesn't exist. Whenever I say 'God doesn't exist', I merely voice my (strong) beliefs that one cannot know, and therefore, the whole point is really technically moot. I can and will not believe in what I cannot directly see, feel, touch, or measure in one way or another.