I have discussed this before. in The problem with atheism where I concluded that an atheist is someone who thinks that god is irrelevant. To make this slightly clearer here, I would say this is an operational definition, an atheist is some who does not employ the premise "god exists" in any of their reasoning or actions. I prefer this to a statement of belief, because that grants too much to theists, they over-emphasize the importance of belief Still based on that operational definition an atheist is some who holds that the proposition "at least one god exists" is most likely false. "Most likely false" as in sufficient not to need to employ the premise in any reasoning or action, or as I said, god is irrelevant. Alonzo Fyfe has a similar post on this topic yesterday,What Atheism Is Not and he makes some additional and interesting points.
According to the wikipedia:
The suffix -ism denotes a distinctive system of beliefs, myth, doctrine or theory that guides a social movement, institution, class or group. For example, baptize (literally derived from "to dip") becomes "baptism," a distinctive system of cleansing in water to testify to the forgiveness of sins... Its usage has since been extended to signify the ideology or philosophy surrounding the element to which the suffix is added. Its usage has since been extended to signify the ideology or philosophy surrounding theelement to which the suffix is added.Atheism is a little peculiar in the company of other isms, closer to baptism than any ideology or philosophy. This might be made clearer by comparing it to theism simpliciter. This asserts that the propostion there is at least one god is true, whereas atheism asserts the proposition there is at least one god is false. It does not tell you very much about anything else at all, does it? This is because neither is an ideology.
Now compare Evangelical Christianity to, say, Randian Objectivism. These are both ideologies and comparable, one can examine the similarities and differences, The former does have theism as a component with a quite detailed elaboration of what is meant by god, whereas the latter does have atheism as a component and elaboration of other ideas, but nothing more to say about the atheist proposition, what could there be? Maybe we should examine what an ideology is.
According to the wikipedia
An ideology is a set of aims and ideas, especially in politics. An ideology can be thought of as a comprehensive vision, as a way of looking at things (compare Weltanschauung), as in common sense (see Ideology in everyday society below) and several philosophical tendencies (see Political ideologies), or a set of ideas proposed by the dominant class of a society to all members of this society. The main purpose behind an ideology is to offer change in society, and adherence to a set of ideals where conformity already exists, through a normative thought process. Ideologies are systems of abstract thought (as opposed to mere ideation) applied to public matters and thus make this concept central to politics. Implicitly every political tendency entails an ideology whether or not it is propounded as an explicit system of thought.This should make it quite clear that atheism is not an ideology, it is at best a component of a wide range of ideologies, bu then so is theism simpliciter too.
The category to compare an atheist to, if that is the position they are taking in a debate or conversation, tacitly or explicitly, is that of a theist. It is a category error to compare them to a worldview. If someone is arguing from a particular worldview, such as Randian Objectivism, then that is comparable to say, Evangelical Christianity - they are both worldviews. It must be noted that often a debate is entered on just considering the arguments at hand, checking the soundness of the premises , the validity or strength of inferences and minimal positions such as atheism, let alone worldviews, are irrelevant.For example, of course if the premise is over god existing or not, then that atheism is relevant. but if say, god exists is a premise granted for debate, then it is not. It is because of such category errors that I highlighted theism simpliciter to make a distinction from any theistic worldview.
Inferences from Atheism
Fnially one can ask is it still possible to generate a partial or quasi-ideology from atheism, or maybe a philosophy in the worldview sense or at least part of one? This would require noting that it excludes any idea where the premise "at least one god exists" is logically necessary. However it is quite difficult to find any ideas for which this is true. Even some atheistic Buddhists - who say if such beings exist that call themselves god (in anything like the Christian sense) are deluded, unenlightened and incapable of enlightenment too boot - can have a form of heaven and hell! For sure the idea of eternally torturing innocents with no possibility of reprieve is one. Some ideas such as the resurrection are quite common without requiring anything like a Christian god, indeed scientists are investigating the possibility, it is called cryogenics Okay, lets not go too far, I am not going to labour this point. Obviously there are specific theological concepts that pertain to a single or group of religions that no-one would expect anyone else to hold such as the Triune God, but those are inherently theistic anyway.
So apart from obvious concepts like that, there seems to be very little that can be determined from this concept alone. To make this clearer ghosts, aliens, souls, dualism, parascience, astrology, homoeopathy, divination, supernatural, superstition, free will, consciousness, reincarnation, morality, meaning, ultimate good to name but a few are not excluded by atheism. What one does know if that any of these or similar items are argued for, then god is not used as a premise. So there is not much one can learn of an ideology, philosophy or worldview purely based the premise "at least one good exists" is false.