In the absence of any positive reasons to believe, I never had to resort to negative arguments, personally. Like many longtime atheists, it took a lot of fundamentalist theocratic imperialism to get me to worry about it at all!

If I had to frame an argument, it would be historical: among desert tribes, in the absence of governments as we know them, religion was the primary source of social coherence i.e. the government. Once you realize this, and see that we potentially have progressed beyond that level, the "argument from tradition" falls flat.

Example: when it was discovered that pork was a health hazard, before people learned to cure it (or refrigeration), how did you spread the word and enforce it? By making it a "command from God": "Thou Shalt Not Eat Pork". It saved countless lives over the years, but now we're much better at taking care of our food, our health standards, our governments, and our lives. We just don't need that heavy-handed theocracy any more, we've (mostly) outgrown it. Right? Unfortunately, this is the way things are still done in the Fundamentalist world-view - whether Muslim or Christian.

The history of god belief. By this, I mean the historical record of the creation of religious beliefs.

Basically, religious beliefs seem to have an evolutionary pattern. Just as other areas of human study and interest have an evolutionary pattern where information is discarded, edited, added to and poked and prodded until it reflects the culture, geography and the politics from which the belief has its roots.

God belief or belief in invisible, supernatural forces had its origins in primitive explanations for the phenomena demonstrated in the natural world.

So, some of the first explanations for the inexplicable demonstrations of the natural world were animistic. That is, that powerful, invisible supernatural forces were present in living and non-living things. So, a rock which may have a specific property which didn't have a scientific explanation - say pumice, which can float under certain circumstances, would be attributed with "special powers" that other rocks did not have.

People may also have recognized the "floating quality" of pumice and decided that by wearing it, they would not drown. So, objects became talismans to ward off the obvious potential dangers which come about from living in a natural world.

The wearing of talismans is a form of fetishism. Where the object worn is believed to have special magical powers. A lucky rabbit's foot is a form of fetishism. Supposedly it inherently wards of bad luck because of some unknown but assumed property associated with "fleet of foot." So people believed that as the rabbit was fast and elusive, so could they evade bad luck.

As people became more tribal, more specifically cultural in their beliefs, they created totems which represented the "special forces" which protected their tribe. So, the attributes attributed to various living things and non-living things became part of religious rituals which became tribe specific.

Consequently, the totem animals of the early peoples in North America, differ greatly from the animals to which the Australian aborigines attributed special powers.

The evolution of the belief in "special powers which exist in nature which could be harnessed by humans to solve human problems is continued through the processes of theriomorphism, zoomorphism and anthropomorphism.

Essentially, where there has been an intangible, unknown condition, human beings have artistically invented explanations which ease their existential angst. (anxiety about life and their existence)

The concepts of god have expnaded with our expanding knowledge, and lack of knowledge of the universe. Where once, there were many separate discrete "forces" which competed for power and influence over humans, now we have aggregated them into one explanation - the concept of monotheism.

Where once there may have been a hierarchy of gods, (and still is in polytheistic religious belief), there is now a preference for a "god dictatorship" or monotheism.

Where once, the inexplicable was attributed to many separate, discrete "forces", it is now attributed, in the main, to one supernatural force.

Our concepts of the supernatural and god may have expanded and evolved with our increasing knowledge, but they remain deeply rooted in our origins, where they were, to put it simply, "artistic inventions" of a creative, evolving mind which sought to explain the unknown.

Once I stopped believing in Santa Claus, and realized that my parents had lied to me about him, it was a small step to entertaining the possibility that God was similarly non-existent.

The whole idea of a God is stoopid.

The idea that reality is socially constructed. By the time a baby makes its first thought it has been trained to use the proper symbols. By the time it knows its name it is deep inside the walls of culture where the more one thinks the more enveloped in cultural symbols one becomes. There is no way out; not even a glimpse.

Is this an argument for or against the existence of God? Indeed.

Not an argument but just the observation that a lot of people will earnestly and confidently aver things, which indisputable evidence later shows to have been wrong--or that people will earnestly and confidently contradict each other--or commit cruel injustices...even to people they love. Or that I've trusted people with claims that I ought to have recognized as incredible, had I been considered them clinically, impersonally and independent of my desire to be a particular person's friend or to be in step with a group. Self-deception and cooperative credulity came to seem the norm. Plus religion itself is so clubby, and every sect seems to believe that the other's going to hell or otherwise deep in the divine doodoo.

Social studies class in middle school. We were doing a unit on Greek and Roman mythology. I don't think the textbook stated it explicitly, but I learned that "mythology" was the word we used to describe religions people no longer believed in. I took that and flipped the logic and came to see religions as mythologies that people still believed in.

Now that is just an argument against religion, though. I know that there are more deistic ideas about gods that escape the above. I do not just ignore these ideas. To me, a deistic universe makes about as much sense and has about the same probability as a computer-simulated universe or an endless series of alternate universes. There are more possibilities than that, of course, I just picked two examples that I often use.

What I've noticed is that most people who believe in a god or gods don't mean it in any kind of deistic way. They want a loving, judging, testing, protecting, football game deciding, maintaining of an eternal afterlife, can excuse for all the bad things in life whist crediting for all the good stuff, meddling in human affairs overtly (a long time ago) and covertly (nowadays) kind of god or gods. And I just don't see any evidence for that. Believers can quote evidence, sure. But believers of all religions can do that, and according to most of them, they can't all be right. But they can all be wrong.

I guess what I'm driving at is that I don't believe in religion because it is all so obviously made up and I don't believe in any gods because that hypothesis doesn't have any outstanding body of evidence behind it to distinguish it from the alternatives.

For me it was the argument from evil that lead me to question my (albeit poorly formed) faith, and that faith was dealt the killing blow by the argument of incoherence (I see the two arguments as intimately related).

A reverse epiphany at 15 from which I've never looked back.

From my book: When we seek for a cause of it all we run into absurdities, precisely because blind chancistic events cannot be figured out! Chance events can produce order. We know this. Even if the odds are extremely unlikely for this universe to exist, once there is some order in the universe and someone to look upon the order that's there, it cries out for an explanation. So we try to explain it, but fail time and again. Pascal would be right here to say all over again, "I look on all sides and see nothing but obscurity; nature offers me nothing but matter for doubt." We may even have to say, like I had previously said, that it cannot be figured out with reason, and initially it can't. But when we reflect on why we can't figure it all out, the best reason I can offer is that random chance events can't be figured out hindsight."

See here.

I found my epiphany at the age of 24 and turned from a belief in God. How coud He(being perfect) not see Satan coming? and why not spare the dramatic battle (at Man's expense) to prove Satan wrong? But without a spiritual purpose my life proceeded to detirorate. Finally at the age of 40 I was touched by God, or atleast his presence. I cry now when I think of intelligent people like you who do not know Him, and the good you could do for the world he gave us when you seek his righeousness. I am ruined for anything else in this world but to serve such a loving being. I love you and pray right now you will be visited .... beleive me after that, your first epiphany will seem so selfish you will cry for days knowing his love never ceased for you. And the true epihpany is that it is He, not I nor you, that truely matters. Yet God has a purpose for us all. I Pray with sincerity and faith that you may find yours.