Why are atheists atheist rather than agnostic?

Gnostic = Knowledge. Prefix A = Without. Agnostic = Without knowledge

Theist = Belief in god(s). Prefix A = Without. Atheist = Without belief in god(s)

Gnostic/agnostic has to do with what you know. Theist/atheist has to do with what you believe.

Gnostic theist = Claims knowledge of god(s) and believes

Agnostic theist = Claims no knowledge of god(s) and believes

Agnostic atheist = Claims no knowledge for (non-existence of) god(s) and does not believe

Gnostic atheist = Claims knowledge for (non-existence of) god(s) and does not believe

Agnostic and atheist are not mutually exclusive.

Title question and question repeated at the end: because atheist and agnostic are two separate things. Atheism deals with the lack of a belief in a god or the belief that there is no god (weak atheism and strong atheism respectively). Agnostics claim to not know if any gods exist. Some actively try to seek the answer, some claim that answer is unattainable. There are Agnostic Atheists who acknowledge that there is no evidence either way, but don't believe that a god exists.

Concerning the first paragraph: While there isn't proof that gods don't exist, there isn't proof that any exist either. For Yahweh/Jehovah/God, whichever name you wish to endow the god in the bible with, the problem with his existence is that he is based on older gods (study its history) from the Sumerian and Babylonian myths. The god that Christians of various denominations worship seems to be based on the god Enki in particular. The events in the creation event described are a rough variation on Enuma Elish as a set of six and rest on the seventh are common in both. One is six generations with the sixth making man so the seventh can rest, and the other is God making everything in six days and resting on the seventh.

For the big question in paragraph two, "What is the logic behind atheism?"

For me, I take the strong atheist position. I say that there are no gods because there is insufficient evidence to conclude that any exist. For some, such as Jesus, there are predictions which are made and messiahs fail to fit. (see link in source on this)

"What is the line of logic that leads one to believe "there is no God" over "we don't know if there is a god since one hasn't been proven or disproven"?"

Many of those in earlier civilizations claimed that a god was apparent based on what they knew, saying that those who didn't believe in a god (note, it was always the god that they believed in that they were using as the criteria for a god) were "fools". By today's standards, what they knew wasn't much. A god was used to explain something that they didn't know about, such as thunder, the creation of the world, why volcanoes erupted, and disease amongst a myriad of other observations they lacked a testable answer for. Many of those we've been able to become able to disregard, such as the Hindu pox goddess Shitala Devi for an explanation of disease, the Hawaiian goddess Pele for why volcanoes erupt, the Norse god Thor for why thunder happens, or the Greek god Poseidon for why the oceans act in the manner that they do. All of these events and observations, we have explanations for. Any other claim concerning what a god has done is apt to see another face the same fate as our species' understanding of the universe in which we live develops, until the only claim that could be made about any god in question exists outside of time and space and cannot be observed, leaving it as an idea that can't be proven or falsified.

Fundamental Logic Fail: There's no proof that ANYTHING does not exist. You can't go through life under the assumption that EVERYTHING just might exist. At some point you've got to categorize things into real/not-real. If evidence is presented that moves something from one category to the other then so be it. To maintain a position despite evidence to the contrary isn't atheism, it's dogmatism.

In reality, there is no difference between between agnosticism and atheism. The atheist doesn't believe there is a god or gods. Show me irrefutable proof of a god and I'll believe there is a god (just don't ask me to worship it).

1. Why are atheists atheist rather than agnostic?

A: Because they have sufficient data/observations to lean on the probability that god doesn't exist.

2. I became agnostic realising that there is no proof that God does not exist

A: There is also no proof that the boogie man doesn't exist - I suppose we should all be boogie man agnostics? Or does a god that might or might not exist have exemption from this type of logic?

3. I was perfectly content with that.

A: Your content-ness is nothing more than microscopic chemical output with your brain, having no significant representation of reality.

4. Agnosticism is clearly the most logical belief system

A: Refer to point # 2, you can't prove any imaginary being exist - so that means we should be agnostic in all these cases? There might be alien life forms living inside your eye, there might not...better be agnostic about it, it's much more rational than assuming (or saying you know) there are no aliens inside your eye.

I am a true athiest and have never and never will question that there is a god. Do you know why.

If god did exist, would he make us be at war with each-other so we can wipe ourselves from existence.

If god did exist, would he list people in the bible who he thinks are wrong and put them on this earth to be verbally and physically tortured by religious extremists.

If god did exist, why would he be such a bastard.

I am a full blooded atheist, who supports anyone who is looked down on by religious oppression, (etc. Blacks, Gays, Minorities of society, and of course, other atheists), and guess what, I have made this decision and I am only 13 years old. Do you know why I have made this decision so young, because I am wise enough to make the right decision, and smart enough to realise that religion is the evil of this planet. I am an atheist and I'm damn well proud of it.

Either you believe in a God or you don't. If you don't, you are an atheist.

When someone offers a reason to make the hypothesis of a God, then theism and agnosticism are on the table. So far, that hypothesis is completely unnecessary, and thus unwarranted.

edit: I know there is no God to the same level of certainty that I know there is are no leprechauns, no fairies, no Sasquatch, etc. We do not require 100% certainty to make a knowledge claim, or science would be impossible.

Atheism and agnosticism are not mutually exclusive. They are not on the same spectrum. Atheism is a position on belief (the lack of a belief in gods) while agnosticism is a position on knowledge (the lack of knowledge about god). I am both an atheist and an agnostic.

I am an atheist-agnostic to most deities. I am atheist-gnostic to impossible gods, such as the Judeo-Christian deity.

"Agnosticism is clearly the most logical belief system"

*laughs* It's not a belief system.

Agnosticism is the lack of knowledge or certainty that there is or is not a god. It's not a middle or third position.

For me personally I know there isn't a god, it doesn't make sense for there to be someone or something in control of all of this. We don't need a god. We are born, we live, we die, we are buried/cremated and become part of the earth again. I think that is the most beautiful cycle there is, why does there need to be anything more than this? What more could you possibly need to justify your existence?

On another note, I know god doesn't exist because of a massive long list of terrible horrible unfortunate things that have happened to this planet and the people on it, we have done that, and we have to take responsibility for that, if there is a god, like people think there is, he's watching a hell of a lot of destruction and most likely waiting for us to wipe ourselves out. That doesn't sound like the god I've heard about?

For me: not knowing (agnosticism) + no likelihood of existence = atheism.

Same deal for unicorns, I can't know for certain that they don't exist but the likelihood is sufficiently small that I'm comfortable believing that they don't.

Find me something for which there is inconclusive evidence for and I'll be agnostic about it.

By your reasoning all theists would have to accept that all deities could possibly exist, which clearly very few theists are prepared to do.