(and why I find myself unable to believe in a certain kind of supreme deity)
"Is God willing to prevent evil, but not able? Then he is not omnipotent.
Is he able, but not willing? Then he is malevolent.
Is he both able and willing? Then whence cometh evil?
Is he neither able nor willing? Then why call him God?"
-Epicurus
I don't believe that an omnipotent, omniscient, omni-benevolent entity is compatible with my observations of the world. It all has to do with the Problem of Evil. If the above quotation didn't clue you in, and you're not familiar with it, the Problem goes a little something like this:
1) God is said to be all-powerful.
2) God is said to be all-good.
3) A good person would oppose and try to eliminate evil.
4) Evil exists.
5) Therefore, if God exists, God is either not all-powerful, not all-good, or both.
Most objections that I hear to the Problem of Evil involve free will, or suffering building character, or it all being part of God's inscrutable plan, or something along those lines. To which my response is "what part of all-powerful don't you understand?" An omnipotent being makes the rules. There is no "only way" for an omnipotent being unless that being wants there to be an only way. It is entirely possible for an all-powerful being to eliminate evil without eliminating free will; we mortals might not know how such a thing is possible, but an all-knowing being surely knows how it is possible, and an all-powerful being surely has the power to make that possibility a reality. The same goes for building character or accomplishing whatever God's divine plan may be: an all-powerful God has the power to do such things without including suffering, pain, darkness, and evil.
Other, less frequently encountered objections include:
"Good is by definition God's will. Therefore, anything that God allows or wills to happen is good. Things we may consider evil are actually good, because God wills them to happen or allows them to happen."
and, along the same lines,
"How can we pathetic finite mortals judge the infinite perfection that is God? He's further beyond us than we are beyond bacteria, but we'd never accept a bacteria's definition of good."
or, even,
"God created us. If he chooses to destroy us, that's no more evil than a potter deciding to destroy faulty pottery."
Now, personally, I think these arguments are a little silly, but I've encountered them more than once, so someone out there must take them seriously. The first objection is pretty much stating that there is no such thing as evil; really, if anything that happens is God's will, and good=God's will, then everything is good. Genocide, war, natural disasters, crime of any sort . . . all as good as the most noble, selfless acts. Good becomes meaningless. As for the second objection, I sincerely doubt there are many out there who suppose that we humans are infinitely good and infinitely powerful. If we were infinitely good and infinitely powerful, though, one supposes that we could and would eliminate all forms of evil, including those forms of evil that affect bacteria (or ants, or viruses, or whatever "lesser" you feel like using in analogy). And, with the third objection, just for fun replace "potter" with "parent" and "pottery" with "children." Makes it a little different, neh? Now replace "potter" with "infinitely powerful being" and "destroy faulty pottery" with "destroy things he created and could make better in an infinite number of ways without destroying them." Because that's what we're really talking about. An anology is just a picture of something; it's not the thing itself.
Understand, I'm not trying to disprove the existence of the deity of the Jews, Christians, and Muslims. Rather, I'm saying that if such a being exists, it's extremely unlikely he exists in the way he's sometimes described, i.e. all-powerful, all-knowing, and so on.