Nobody should hold forth on this topic who hasn't read Bertrand Russell's essay "Am I An Agnostic Or Am I An Atheist?". Have you seen it? It was the first thing I devoured when I began flirting with the devil. Below is an extract of the most germaine parts but you really owe to yourself to read the whole essay:
Proof of God
Here there comes a practical question which has often troubled me. Whenever I go into a foreign country or a prison or any similar place they always ask me what is my religion.
I never know whether I should say "Agnostic" or whether I should say "Atheist". It is a very difficult question and I daresay that some of you have been troubled by it. As a philosopher, if I were speaking to a purely philosophic audience I should say that I ought to describe myself as an Agnostic, because I do not think that there is a conclusive argument by which one can prove that there is not a God.
On the other hand, if I am to convey the right impression to the ordinary man in the street I think I ought to say that I am an Atheist, because when I say that I cannot prove that there is not a God, I ought to add equally that I cannot prove that there are not the Homeric gods.
None of us would seriously consider the possibility that all the gods of Homer really exist, and yet if you were to set to work to give a logical demonstration that Zeus, Hera, Poseidon, and the rest of them did not exist you would find it an awful job. You could not get such proof.
Therefore, in regard to the Olympic gods, speaking to a purely philosophical audience, I would say that I am an Agnostic. But speaking popularly, I think that all of us would say in regard to those gods that we were Atheists. In regard to the Christian God, I should, I think, take exactly the same line.
Skepticism
There is exactly the same degree of possibility and likelihood of the existence of the Christian God as there is of the existence of the Homeric God. I cannot prove that either the Christian God or the Homeric gods do not exist, but I do not think that their existence is an alternative that is sufficiently probable to be worth serious consideration. Therefore, I suppose that that on these documents that they submit to me on these occasions I ought to say "Atheist", although it has been a very difficult problem, and sometimes I have said one and sometimes the other without any clear principle by which to go.
When one admits that nothing is certain one must, I think, also admit that some things are much more nearly certain than others. It is much more nearly certain that we are assembled here tonight than it is that this or that political party is in the right. Certainly there are degrees of certainty, and one should be very careful to emphasize that fact, because otherwise one is landed in an utter skepticism, and complete skepticism would, of course, be totally barren and completely useless.
Persecution
One must remember that some things are very much more probable than others and may be so probable that it is not worth while to remember in practice that they are not wholly certain, except when it comes to questions of persecution.
If it comes to burning somebody at the stake for not believing it, then it is worth while to remember that after all he may be right, and it is not worth while to persecute him.
In general, if a man says, for instance, that the earth is flat, I am quite willing that he should propagate his opinion as hard as he likes. He may, of course, be right but I do not think he is. In practice you will, I think, do better to assume that the earth is round, although, of course, you may be mistaken. Therefore, I do not think we should go in for complete skepticism, but for a doctrine of degrees of probability.
I think that, on the whole, that is the kind of doctrine that the world needs. The world has become very full of new dogmas. The old dogmas have perhaps decayed, but new dogmas have arisen and, on the whole, I think that a dogma is harmful in proportion to its novelty. New dogmas are much worse than old ones.
http://www.positiveatheism.org/hist/russell8.htm
Topic: Understanding Agnosticism