I dont care about metaphysics. Metaphysics is the study of those things which can be said to exist beyond and outside of the physical reality we experience through the senses, memory, feeling of consciousness etc. I dont think debates on metaphysical questions can be productive, primarily because there is no way to present evidence or arguments about things we cannot experience in any way. I'm not interested in arguments about the idea “gods exist” if those gods cant be observed. There's no way to know anything about such beings, so any debates about them cannot conclude. This is not to say I dont have metaphysical opinions, I'm a mathematical Platonist, I believe that abstract mathematical ideas like the number 7 or triangles can be said to have some kind of existence beyond any particular collection of 7 things or any drawing of a triangle. I dont try and argue with people about this, because I dont think that belief is meaningful. It's a reflection of my own emotional response to mathematics, there no argument I can give to show I'm correct, or evidence I can show.
That aside, let me turn to gods. I am an atheist about metaphysical gods. The existence of a god beyond this world doesn't fit with my emotional response to the world. This is not an argument, if you do believe in such a god, I dont think we disagree. I dont think there's a real difference between a world with a purely metaphysical god and one without. I dont care to change that belief, I dont care for arguments trying to change what I think. I have many friends who believe in such a god, and I dont think there's anything they believe that I could sensibly argue was wrong. I am agnostic about such gods, because I dont think there is anything here about which one can have knowledge (a-gnostic: without knowledge). I am agnostic in the 50:50, have no basis for a decision one way or the other sense. To say I am closed minded about this misunderstands, I dont think I know the right answer, I think there is not a right answer to know.
However. There is another sense of the word god, another sense of agnostic, another sense of atheism. Interventionist gods are beings which affect the physical world. Specifically they change the world in a way that shows that they care about life (generally, humans in particular). I've deliberately defined this in a rather broad way. Under this heading I include immensely powerful but totally physical beings like Lovecraft's Cuthulu or the Doctor, along with beings that exist outside of space and time, but which occasionally reach in a change things, the Greek pantheon as a classic example, a final thing of this kind is the cosmic watchmaker, a being who creates the universe, sets all the laws of physics in place with the aim in mind that life should grow and develop. I think this is a being whose existence can be argued about, there is evidence that could show this being to exist or not. There are many people who believe in one kind of god and not the other, there are deists who believe there is a god but that it has no influence on the world, there are people who belive in a god, but an entirely physical one.
About this second kind of god I am an atheist. I think that a universe designed with life in mind would not look like this. It wouldn't be mostly empty and useless to life. It wouldn't be almost guaranteed to kill any lifeforms that left the safety of a planet. And there would be far more planets that could support life. I think a universe designed with life in mind wouldn't end (as this universe will) with all matter falling into a vast number of black holes and ending up cold dead and empty. I dont think that a universe where gods influenced the outcome of wars would really have a history like ours. I dont think a universe where illness was caused by the vengeance of angry gods would have such perfect correlation between public heath and pandemics. I dont think, in short, that this looks like a universe that anyone cares about apart from us humans.
However. About such gods I am also agnostic. I dont think that I have an absolute truth, I dont think I can prove my belief like I can prove Pythagoras' Theorem. If there was some way in which I was convinced that either such a god existed or Pythagoras' Theorem was false I would be obliged to accept such a god. I am not closed minded about this, I have however made my mind up. These are not incompatible, it is possible to hold a belief without being mathematically certain of it. After all, I believe quite strongly I am sitting on a chair, but, I'm not looking at it, it could well be that someone broke into my room as I was sitting down and replaced it with a carefully posed flamingo. If I stand up and look at this flamingo I'm not going to steadfastly believe that it is in fact a chair, but that doesn't mean I'm going to keep checking it to make sure.
There are two senses of agnostic, either claiming no knowledge or even strong belief can ever be justified in any way, or to claim that you cant be perfectly mathematically certain beyond any possible doubt. Both are valid in their own domain. To claim the first kind refers to physical facts is nonsense, evidence about the physical world exists in vast and fantastic abundance, we can know lots about the physical world with 99% certainty. To claim that we cant be perfectly mathematically certain about metaphysics is true, but not nearly strong enough to express our profound ignorance of anything beyond the physical. And like almost all atheists who have ever existed, I'm an agnostic in the sense each god demands.
I am then an agnostic, but I never describe myself as an agnostic, why? Because I take agnostic as read. I take it as a given that we can know nothing at all or have any evidence about metaphysics. I take it as a given that no physical theory will ever be 100% perfect, that we can never have perfect knowledge of the physical world. I take this as a given in everything, so I dont feel that saying it makes a contribution. If someone asks me who the Prime Minister is it doesn't help me or them to say that I cant be 100% sure that I haven't just misheard every time someone mentioned Gordon Brown. It helps them to say that it's Gordon Brown, we can take the 0.0001% uncertainty in this statement as read. Likewise, if someone asks me if I believe that 1400 years ago a man road up heaven on a winged horse I say no, I'm an atheist, the fact that there is a minute possibility of a horse with a fantastically rare mutation having ridden a man up to the sky can be taken as a given and doesn't help.