In a nutshell, it’s because no one knows how to define anything. Just look at how fuzzy the common terms are:
- On one side, we have “theism”. The belief that God exists. Or a God, anyway - we could be talking about someone who believes in the existence of Zeus on Mount Olympus. A theist can also be believe tat God is merely “the thing that created the universe”, which can conceivably be a form of energy or mathematics itself. It’s usually assumed though that the discussion specifically relates to the God of Abraham. Or maybe not so specifically… after all, in the eyes of a theist, the God of Abraham may or may not be all loving, may or may not be all powerful, may or may not be all knowing, may or may not answer prayers, may or may not directly intervene in human affairs, may or may not cause miracles, may or may not be a fan of George W Bush, and may or may not be some combination of a father, son, and holy ghost. Different combinations of those properties make for 1,024 different possible versions of the God of Abraham right there that we might be debating the existence of. Very few people, theists and atheists alike, put very much thought into what exactly they’re defending or attacking, resulting in debates where either side will just change their working definition when they run up against a logical argument they can’t defeat.
- On the other side, we have atheism, which itself is divided into (at least) two camps. “Weak atheism”, which corresponds to “I don’t believe there is a God”, and “strong atheism”, which corresponds to “I believe there is no God”. Note the difference - one is simply a statement of disbelief, the other makes a positive assertion of nonexistence. But most people don’t even know that distinction exists, not even self-described atheists. Theists tend to assume (or at least, argue based on the assumption) that all atheists are of the strong variety, ostensibly so that they can make the counterargument that atheism is just as much a “faith” position as theism. However, the reality is that most self described atheists are of the weak variety. Further confusing the issue, a lot of weak atheists describe themselves as “agnostics”, which is a misstatement of their actual beliefs.
- Which brings us to agnosticism, which (in my experience) is the one that’s the least well understood; the average joe seems to simply interpret it as a more politically correct version of atheism. But agnosticism actually has nothing to do with a belief in God, instead concerning itself with the knowability of God (it literally means “without knowledge”). And even in this case, there’s at least two flavors: “We can’t know” (God is outside space-time, we can’t test for him), and “We don’t know” (We could theoretically find out, we just haven’t as a practical matter). Wikipedia also adds “I don’t care” and “The question is stupid” as agnostic positions. But the bigger point is that it’s completely independent of theism or atheism. You can be an agnostic theist: “I don’t believe we can know that God exists but I believe that he does exist” as well as an agnostic atheist: “I don’t believe we can know that God exists but I believe that he does not exist”. Since very few people on either end of the scale claim absolute certainty about the existence or non-existence of God (whatever flavor they’re talking about. the vast majority of people are some flavor of agnostic.
Personally, I hold any given definition God to the same standard of evidence that I do Santa Claus, celestial teacups, and leprechauns. So in general, I view most conceptions of God the same way I do Ether and the Caloric Theory of heat; a victim of Occam’s Razor.
But the keyword in the above is “most conceptions”. I’m a strong atheist with regards to Zeus and the Flying Spaghetti Monster - I positively believe that those Gods don’t exist. I’m a weak atheist with regards to a deistic concept of a God that doesn’t interfere (much) in human affairs - I don’t believe such a God exists. I’m strong atheist if you describe God as “Omnipotent and Omniscient”, or for any other definition that includes logically impossible attributes. If you believe God is “the thing that started the Big Bang”, then I’m a believer - I think *something* kicked it off, after all. If you want to assert “God is everything” or “God is love”, then sure, I can’t discount the existence of those things. I don’t see any real reason to define God that way, but whatever floats your boat.
The thing is, no one bothers to define their terms before jumping into a debate. Too often, an atheist will assume he’s debating a fundamentalist who believes that God answers prayers, the Earth is six thousand years old, and gay sex is the root of all evil. A theist, for his part, is prone to assuming that the atheist believes in science-as-his-religion, and that knocking down any particular scientific theory in the last 500 years is enough to knock down atheism. More commonly, theists assume that the atheist absolutely positively believes there’s no kind of God whatsoever beyond any shadow of any doubt - and he can therefore win the debate just by introducing the slightest doubt.
The truth is that you’d find few people on either one of those extremes, but rarely do you see anyone who bothers to actually state their positions before debating them; they’d rather pat themselves on the back for knocking down strawmen:
“The Earth isn’t really 6,000 years old, so I win!”
“We can’t know what happened before the Big Bang, it might have been God, I win!”
The debates wind up running in circles as one side or the other continually invokes a variation of the True Scotsman Fallacy - “I never SAID God was all loving”, “A true atheist would think this was true”, etc.
I haven’t even mentioned yet the secondary arguments that always come up on internet, which have nothing to do with the existence or non-existence of any sort of God, but one side or the other always brings them up anyway. Stuff like:
- Atheists “hate” God and “hate” religion and “want to ban it entirely”.
- Stalin and Mao were atheists, therefore all atheists are genocidal maniacs (that’s especially a pet peeve of mine, since those are among the most religious regimes ever in every way that matters).
- On the flip side - atheists love to bring up abortion clinic bombers, pedophile priests, atrocities by the Vatican, the Crusades, or any number of other evils brought on by religion.
- Theists “hate homosexuals” or “hate [some other form of sexuality]”
- Theists are all Republicans.
The fact is that none of those things have anything to do with the existence, nonexistence, belief, or non-belief in God. They might have a place in a debate about the merits of religion itself, but more often than not they’re just fallacious arguments, encompassing a number of logical fallacies (not the least of which is pure ad hominem).
The vast majority of theists aren’t fundamentalist Bible thumpers who deny evolution and believe that the book of Genesis is literal truth, but atheists love to assume they are when they start this debate. Similarly, an atheist may or may not believe in science, evolution, secular humanism, rationalism, skepticism, or anything of the sort - in fairness, they usually do, but one thing doesn’t follow from the other. Plenty of theists believe in those same ideas, and plenty of atheists believe in astrology, UFO abductions, and other scientifically indefensible ideas.
So what’s the moral of the story? If you’re going to argue about whether or not God exists, define it first. And then, if you can, stick to relevant arguments. It makes the ensuing debate much better and far more interesting.