For whatever reason, I've somehow become embroiled in a few discussions recently regarding the possibility of God's (or a God's) existence, and I wanted to put my two cents out there to lower the transactions costs of having those debates (that is to say, I don't ever want to have to explain my position on this again). In this post, I'll first offer an intuitive reason why it's not reasonable to be an outright theist. I'll then turn to a discussion of atheism, offering a pair of thought experiments which I believe demonstrate the indefensibility of a strong atheist position. I'll conclude with some thoughts about the agnostic middle ground that's left, suggesting that the position doesn't end up providing much of a safe haven for theists, even though it defeats their principle opponent. In fact, I will suggest that by softening atheism in the ways suggested here, agnostics can actually provide a much more nuanced and fatal critique of religion and theism than ardent atheists can.
The first reason that I find it unreasonable to be a theist is that there is no theistic position which is clearly the most plausible one. I think that most theists are aware that this is true, but I don't believe that they truly recognize the significance of this fact. If one is to maintain belief in a particular account of God, then one is committed to the position that all other theistic positions must have been fabricated by people. That is, if I am a Christian, I am committed to the position that Islam is at least partly based on a fabrication (either by a mistaken individual or by a deliberate act of deceit). (The position of a Christian with respect to Judaism is an exception to this, but I don't think it's unreasonable to view Christianity as a variant of Judaism. Jews, however, are committed to the view that Christianity is a cultural -- not divinely inspired -- phenomenon.)
If it's true that from the standpoint of any given theistic account, it can be accepted that every other theistic account is a cultural phenomenon, then it seems reasonable to conclude that any given theistic account could plausibly be construed as a cultural phenomenon. But if any given theistic account could plausibly be construed as a cultural phenomenon, then it would seem rather unreasonable to select one to elevate to the status of "faithworthy," condemning all others to be mere fabrications. It would seem much more reasonable to conclude, "We have no compelling reason for accepting any one of these accounts; each could be a merely cultural phenomenon."
Turning then to atheism, we have to ask whether the unreasonableness of theism gives us reason to believe that there is not a God. And it seems like a fair answer is "Well, if we can say that every theistic account can be understood perfectly coherently as a cultural phenomenon, then doesn't it seem likely that there isn't actually this mysterious and powerful being out there, and that the real explanation for the widespread belief in a God really is just that religion is a cultural phenomenon?" And to be honest, I don't dispute that point. But a question remains: could a God exist?
And on this point, the atheist (if she is going to call herself an atheist, and not an agnostic) would seem to have to reply with some sort of explanation for why a God does not exist. But what kind of evidence could someone have for such a claim? As we have all had drilled into our heads, the absence of evidence is not the evidence of absence. It's pretty darn hard to prove that something doesn't exist. The only way I know of to do it is to prove that it could not exist; that there's something about the concept of the thing, or about a completely uncontroversial fact about reality, that is simply incompatible with such a thing existing.
Now, there are a bunch of reasons someone might offer as to why a God-like being couldn't exist, and I think it would probably be foolish to try to figure out what they might be and evaluate them one by one. So instead, I'm going to offer a pair of explanations for how something that I would be comfortable calling a God could possibly exist. Of course, these are simply thought experiments; I'm obviously not claiming that this will demonstrate God's existence, or even that if God did exist, one of these explanations would be the correct account of God's nature.
With those disclaimers aside, the first possible explanation goes like this. We currently know a lot about the kinds of things that exist in our universe, but there is a fundamental limitation on our ability to learn everything. That limitation is that the only kind of thing that we can detect is the kind of thing which directly interacts with physical matter, or which interacts with something that interacts with physical matter. That's why it can be so difficult to understand how things are composed; we need to somehow be able to detect stuff, and often that's not so easy. Neutrinos, for example, gave scientists fits for decades, and as far as I know, we still don't entirely understand what their deal is. So it's entirely possible that there's a kind of thing out there in our physical universe which we don't know about yet (and maybe never will).
I take it to be possible, that there is a type of thing in our universe which is composed of something which we do not yet know to exist, but which has the core properties of a God. For example, it's possible that such an entity could actively convert something we don't yet know about into energy or matter (I recognize that this would violate "laws" of physics, but those laws are based on an assumption that we know all the kinds of things that exist, and that assumption is technically not true), and could affect change in the material universe in a way that would violate the laws that govern the interactions of material objects. If such an entity existed, the basic concept of a God, I think, would be fulfilled: it could have created everything in the material universe, it could have powers that violate the laws of material physics, it could have the capacity to infallibly predict the consequences of interferences with the material world, it could have been responsible for the emergence of life and/or mankind, and it could even have been behind the development in humans of a moral faculty.
I see no reason to believe that such an entity could not exist. It may be argued that theists would not accept this sort of being as their deity, or that theist accounts of God involve the attribution of properties to God which simply make no sense. To that, I respond, "Fine, but the entity I discussed here is Godly enough to me, and I think could fairly be cited by nuanced and intelligent theists as the entity in whose existence they believe." One might persist, though, in arguing that God must have some qualities not captured in the above thought experiment, and on one count, I would hesitantly concede: Most theists believe that God created the universe, and not just all the matter in it. I say "hesitantly" because, well, oh come on! It's frikkin' close enough! But no matter; on to the second thought experiment.
I take it that for all the things we know about our physical universe, we don't know what sort of thing it is, or if it is a thing at all. To call the physical universe a "thing," I think, suggests that it exists in the context of a greater or more expansive sort of existence, which may include other kinds of things. That is, if we can coherently call the physical universe a "thing," then there would need to be some other kind of thing which is not subsumed under the heading of "the physical universe." We might say, "The physical universe exists within the context of a sort of meta-universe, in which other kinds of things exist." Now, trying to imagine the nature of a meta-universe makes my head hurt, but I take it to be possible that it could exist as I have described it -- that is, that other things exist which are not part of the physical universe.
If a meta-universe did exist, it would be conceivable to me that there might be something which is not a part of the physical universe, but which could have the power to create something like a physical universe, and to interact with it once it had been created. Such an entity, it seems to me, could have all the properties discussed in the previous thought experiment, with the added bonus of not having any sort of physical existence, and being the creator of the physical universe. It may be noted that this explanation still passes the buck in an important sense: God created the physical universe, but not the meta-universe, and we would not have provided ourselves with any explanation of how God came into existence, etc. But I take it that this is an inherent problem with theistic accounts: they simply can't provide an explanation of existence that doesn't start with God somehow existing. I say, "Deal with it."
So what are we left with? I've offered a pair of fanciful thought experiments which describe how an entity basically like a God could possibly exist. If there are no inherent flaws in either of them (or even one of them), atheism would not be strictly reasonable: we technically wouldn't be able to say with certainty that God does not exist. But as I said at the beginning of this post, I don't think this is going to be much consolation to theists. We've seen atheism to be mistaken, but in a way that doesn't cut to the core of the position. It's still true that it's unreasonable to place one's faith in any account of God's existence, and even if we can conceive of a being like God existing, it seems much more plausible to me that the reason people believe in such a being can be explained by cultural phenomena, and not the actual existence of a God. This position is technically an agnostic one, but I think that it shares much more in common than the atheistic one it replaces than any theistic account I've ever heard of.
For those who are hesitant to adopt a position like mine on account of faith, let me offer this: There's a lot of great stuff in the Hebrew Bible, in the New Testament, in the Qur'an, or whatever other sacred texts you may study. But recognize that while that's true of the texts you hold dear, it's true of the ones that other religious groups study as well. Seeing religion as likely being a cultural phenomenon does not force us to abandon the teachings of our ancestors, or to condemn as mere mysticism the profound insights about life that have been passed down to us in the form of sacred texts. But what it does do is allow us to criticize our ancestors' views as perhaps having been mistaken, rather than misinterpreted or garbled. We can say that there really isn't anything wrong with homosexuality, and that the biblical condemnations were representative of an indefensible prejudice. We can say that it's really not necessary to avoid contact with women when they're having their periods, or that eating milk and meat in the same meal is really no different from an ethical perspective than eating them separately. We can say that Moses' purge of unbelievers during the exodus was barbaric. We can say that God's actions in the book of Job are deplorable.
And that's a good thing, because it allows us to be honest with ourselves and to trust in our ability to tell right from wrong. It encourages us to be open to ideas from other religions and points of view, and permits us to question what we believe. It forces us to listen to our religious teachers as representing opinions, and not the undeniable truth. It makes us think for ourselves.
In closing, I want to suggest that it's difficult to believe that a God worth worshipping would want us to ignore the evidence we have before us and to blindly accept what we're told. I think that if there is a God, He would want us to take the path described here.