Why Agnosticism?

[diffidus]

However, even on this definition, if you do not know whether God exists or not then there is no firm basis for rejecting the idea and, therefore, the act of rejecting must be based upon an act of faith.

You don't need any knowledge or understanding to lack belief in something. We all lacked belief in god from birth. Babies are too young to understand and take things on faith, yet they lacking of belief in god (according to you) is faith-based?

You lack belief in Santa do you not? Would you also say that lacking belief in Santa Claus is also faith-based?
I lack belief in god due to lack of evidence and credibility. I do not believe in god. I really don't think that such a being exists, but at the same time, I don't claim to know that there isn't such a thing. I just can't bring myself to believe in it.

Science often rejects claims, it doesn't do this with faith. If you claimed there were pink elephants hiding under the moons surface, this claim will be rejected unless you can support the claim.
Theists make the claim that a god or gods exist but fail to support such claims. So I reject their claims as nothing more than baseless assertions. Rejecting the claim that a god exists is not faith-based.
Do you not reject tooth fairies? Do you not reject magical pixies? Do you not reject magical flying rabbits?
We don't need absolute knowledge to reject an idea or claim.

Your argument regarding babies does not count. This is because babies are not aware of the concept of God. It is clearly non-sensical to ask someone if he believes in a concept he has not heard of.

I think your argument about magical pixies and pink elephants is just the usual attempt to trivialise a serious point. I find this argument crops up a lot in this forum and it is a pity, since there is a clear difference between a concept that billions of people claim exists and one in which nobody would assert.

I do agree with your last point: you do not need absolute knowledge to reject an idea or a claim but, if you do not have this knowledge, then you are making a judgement which is based upon incomplete knowledge which absolutely requires belief. In effect, what you are doing is, given your state of knowledge, you think it extremely unlikely that the concept God exists in reality and therefore you form the belief that He doesn't. This is a valued judgement and could possibly be hopelessly wrong.

I would sincerely like to declare myself an Atheist, but because of these (admittedly slightly academic) difficulties I would feel it a compromise to adjust my position from Agnostic, in a sense, almost committing the same sin as religious brethren.

I must admit, however, that I am decidedly more atheist than theist.