Okay, now, at this point, you might be thinking I was just a tad unfair. After all, lots of clever people have thought religion and its metaphysical claims made a lot of sense, so maybe there's more to them than what I'm allowing.
When it comes to the explanatory arguments, the attempts to defend the strategy come out more as attempts to evade the criticism. This is sometimes referred to as the hypothesis of the "god of the gaps". That is, wherever there's something that's difficult to understand or where naturalistic explanations are incomplete, well then, that's because a supernatural explanation is the way to go.
That, to me, exposes how silly this line of argument really is. There's no positive reason to take the explanation seriously; it's all "well, what else have you got?" The lack of a naturalistic explanation actually doesn't imply the presence of a supernatural one. I may not be able to explain the crack in the wall or the noise in the attic, but that doesn't imply they're a portal to another world or ghosts, respectively.
When it comes to the ontological argument, I'm not going to get into the details of all the various attempts to kep that one afloat. Suffice to say, they are very, very complicated. And, to my eye, they don't address the fundamental concern.
That, of course, is the basic emptiness of the concept of the supernatural. Immanuel Kant has a nice way of thinking about this -- he actually uses it to address the god issue. According to Kant, there are the things you know, and then there are the things you can think. What you can know is something you can, at least potentially, experience. If you can't ever have some sort of experience of it -- which boils down, basically, to a perception of it -- then you can't know it.
However, our minds are capable of doing more than simply recording what we find in perception. Our minds can draw inferences from perceptions. And, in some cases, those inferences can outrun perceptions, in the sense that we infer something which, although coherent and apparently sensible, is entirely unknowable because not something we can experience.
One example Kant gives is freedom, in the sense of being free-willed, i.e., being able to make decisions which are your own. As far as he's concerned, and he's probably right, this is not something we can ever know to be true. You can't ever find evidence which shows you that people are free-willed; in fact, if you actually look into the evidence, it starts to look like we aren't.
But, the thought persists. Somehow, we are led to conceive of the idea of freedom. And, even though we can't know that we are free, we are nonetheless allowed to believe we are. After all, the thought makes sense.
That's the key, though. In Kant's system, a thought has to make sense in order for it to be a permissible thing to think, even if it is, strictly, not known. And it seems to me that the concept of the supernatural doesn't even pass that test. So, I can tell you what freedom is like -- it's the ability to make your own decisions, without compulsion from anything else -- but I can't tell you what the supernatural is. Indeed, no one can.
Moving away from Kant, here's another way of making the same point. We can't ever experience a mathematical operation like addition. We can experience instances of it -- here's one now: 1+1=2 -- but the general process of addition is something we have to infer from those instances. So, mathematics is inferential knowledge, not experiential (or empirical) knowledge.
Is the supernatural like that? Is it something we infer from our common experience? Certainly the explanatory and ontological arguments are attempts to infer the existence of the supernatural from common experience. But what, exactly, is inferred?
When it comes to mathematics, I can tell you what's being inferred. What's being inferred is a general rule: in fact, a set of general rules, which are used to manipulate certain symbols (mathematical ones, that is). I don't know what's being inferred when someone says that thus-and-so shows that the supernatural exists.
And, I continue to hold, no one really knows what it is. The supernatural is literally unknowable. To say that the supernatural exists is thus to say literally nothing.
Of course, at this point, religious folks will come back and talk to me about faith, as a special process of knowing which allows us access to the supernatural realm. So that's what I'll talk about next.