I’ve argued before that the problem of evil is unsolvable for a God who is omniscient, omnipotent, and omni-benevolent (http://fensel.net/2011/10/17/why-the-common-conception-of-god-is-impossible/ and further explained in http://fensel.net/2012/04/17/two-logical-notes-on-debates-about-god/).
To get around the problem of evil, a theist or agnostic might not be fully committed to all three omni traits. Maybe God is imperfect, and would rather us suffer from our own choices than have a perfect world. Or perhaps God is perfectly good, but doesn’t have the omnipotent power many theists believe in.
The question is then: what evidence is there for the existence of this type of God? I believe it is plainly obvious that no such evidence exists. I assume most theists believe there is some evidence, though that is a different debate than the one I want to focus on. For agnostics, the general stance is that there is no evidence for or against God. I argue that, if you accept this claim, atheism is the only logical conclusion.
To be clear, atheism is not committed to the view that there is a 0% chance of any type of God existing. We have imperfect minds and very limited knowledge of the universe. It is logically possible that some type of God exists (just not one that has the omni traits). All an atheist needs to argue is that the probability of God existing is very small, and that it is irrational to believe in such a small probability.
Take the agnostic’s starting position: there is no evidence for or against the existence of God. The first issue is that it is impossible to find evidence of a being’s non-existence when that being is not confined to a certain location (Zeus can be disproved by going to Mt. Olympus, God has no such home to be investigated). So, we should be looking for evidence of existence, not non-existence.
If no such evidence is found (as the agnostic starting position holds), the question is then what the chances are that the being exists. It is a huge mistake to think that, since there are two possibilities, there is a 50/50 chance of existence. Take any 4 made up beings: Xenu, the Flying Spaghetti Monster, Ra, and Galactus. If we conclude from the lack of evidence that each has a 50/50 chance of existing, then there is over a 90% chance that at least one of them exists (chance of non-existence: .5 ^ 4). But this is clearly wrong.
The agnostic might just claim that there is no way to determine the probability of God existing. But we do not need to be able to define an exact percentage chance to have a judgment — all we need is a general ballpark for the probability.
Here’s a simple way to think of the probability of God existing. God is a possible entity that could or could not exist. Without any evidence that makes God more likely to exist than other possible entities, God has the same chance of existing as any other possible entity.
So, what are the chances for a possible entity actually existing? In the most basic form, the chances can be defined as: (total number of actual entities that exist)/(total number of possible entities that could exist). To see why this works, imagine somehow being able to see a complete list of all possible entities. You throw a dart and it hits the name “Entity X”. The odds of that entity existing can be determined by figuring out how many of the names on that list actually exist, and dividing that number by the total number of names on the list.
Although we clearly do not know the number of actual or possible entities, we can understand the ratio. The amount of possible entities is at least close to infinite. The number of actual entities, while it may be much larger than we currently can comprehend, will not come close to the infinitely large number of possible entities. The ratio of actual to possible entities is thus incredibly, incredibly small.
The argument for atheism can thus be summarized as:
1. There is no evidence for God’s existence.
2. Without evidence, God is no more likely to exist than any other possible entity.
3. The chance of a randomly selected possible entity existing is very, very small.
4. The chance of God existing is very, very small.
Although this seems like a bold conclusion, it really is intuitive once you remove the unjustified “a lot of people believing in it makes it more likely to be true” intuition. Imagine a being that is like a jellyfish, has telepathic powers, and flies around bringing justice to criminals in some very distant galaxy. While this being is possible, the chances of it actually existing are incredibly small. Same for God — if you make up an entity without evidence, the chances of it actually existing are incredibly small.
Responses to two possible moves made by the agnostic:
1. Distinguish between “logically possible” and “compatible with the laws of our universe”. Perhaps God is not just logically possible, but falls into the more exclusive category “compatible with the laws of our universe”. Does this make the chances of God existing significantly higher?
-While it is a more exclusive category, “compatible with the laws of our universe” is still an almost infinitely large group. So, even if God falls under this relatively smaller category, the chances of God existing are still very small.
2. The “multiple paths up the same mountain” approach. What if God is not just one possible entity, but a multitude of possibilities? Ie, God exists if any one of these thousand versions of God exists.
-Making the term “God” denote a multitude of possible entities multiples the chances of God existing by the number of possible entities God covers. But, even if you multiply it by thousands or even millions, the number is still incredibly small — to think otherwise vastly underestimates the number of possible entities that could exist.