Introduction

By definition, an atheist is simply a person who rejects the idea that there are any gods. Individual atheists can and do differ from one another in almost every other way. However it can help to further classify atheists by examining issues related to god-belief. It is helpful to ask: How many kinds of atheist are there and what are they?

Differentiating between kinds of atheists

Rather than attempt to list the types of atheist as A, B, C and so on, it is wiser to identify the key characteristics that vary.

For convenience, I shall also provide letter codes to designate the forms of each key characteristic.

By upbringing

Fortunate Atheists (F)

These are people who were brought up without religion, and consequently have no religion hindering them from being rational, or embracing science, or rejecting fantasy and pleasant beliefs.

Unfortunate Atheists (U)

These are people who were brought up under the whip of religion, and have spent years in the position of religion hindering them from looking at the world as it is, and were probably discouraged from embracing science while induced to embrace fantasy and pleasant beliefs.

Subtype of Unfortunate: Transient Atheists (Ut)

Some ex-theist atheists call themselves atheists because they want the social status of rejecting religion and spirituality, but in their hearts they still long for the child-like escapism from reality that religion offers. They imagine prophet to be a virtual Harry Potter. They will return to theism in due course, so they are merely Transient Atheists.

Subtype of Unfortunate: Bitter Atheists (Ub)

Some ex-theist atheists are understandably angry about how much of their lives were utterly wasted by focusing on religion and they may have even been victimized by morally-flexible religious practitioners and/or by bigoted believers of competing religions. These atheists feel quite justified to have a chip on their shoulder, and so they are the Bitter Atheists.

By scope

Mono-Atheists (M)

These are people who have fixated on rejecting one specific religion. Their knowledge of other religions is little or nothing. They have not yet reached the stage where they see that other religions are equally deceptive, abhorrent and deserving of rejection. Mono-Atheists tend to be adolescents.
Open-minded Mono-Atheists may hold that present-day religions or monotheistic religions are awful but that some ancient religion or other such as that of the Greco-Roman gods offered more benefit to humanity than downsides. This view is easily dispelled by the evidence.

Superficial Atheists (S)

These are atheists who reject the main end-products of religious reasoning, which is to say the fully-formed religions themselves, but unfortunately not the human tendency toward religiosity i.e. the psychology that is the cause of religion.
They wish to believe that religious thinking goes in one box, non-religious thinking goes in a different box and the two types of thinking never, ever overlap. But the reality is they do overlap a lot.
This binary thinking, i.e. fixating on a yes/no, us/them separation, is an example of reductionist thinking i.e. wishing that a topic is simpler than it actually is. It may be motivated by a fear of deeper consideration or a worry that the problem of fantastical thinking infects many areas, not just religions.
Thus if you propose to a Superficial Atheist that some ideologies or worldviews such as Communism, the Regressive Left, capitalism, or even Neoliberal economics employ pseudo-religious thinking, they will vehemently deny this and may even get angry about any such notion being put forward, because this idea is a heresy spoken to a believer. They will insist again and again that religious thinking is limited to a narrow part of the human experience called religion. See my page on capitalism as a religion.
This behavior is often due to Superficial Atheists having shifted their deep and perhaps unconscious need for religious-like thinking from religion to a particular ideology. They have become ideologues (a different kind of believer) and therefore emotionally invested in the religion-like ideology, such as those mentioned above. They may hypocritically claim to be quite rational while being the opposite and shallow in their thinking.

Realistic Atheists (R)

Realists recognize that the human mind has many inherent failings and that religious thinking will never be limited purely to established religions or to spiritual thinking i.e. to end-products of religious psychology.
People are just people, they make many mistakes of thinking every day and they are easily manipulated. Any ideology or system of thought can be used to brainwash and convert people in the same ways as do established religions. Claims of gods are not a prerequisite.
Communism, regressive-Left, Neoliberal economics, and even capitalism can function as pseudo-religions. They simply offer surrogates to gods, clergy, faith, and unquestionable beliefs.

By consistency

Anarcho-Atheists (N)

These are people who, having observed how corrupt religious authority behaves (lying, cheating, stealing, abusing) have realized that all authority does these things to some extent and that it would be inconsistent, disingenuous and hypocritical to only reject religious authority without also rejecting similarly awful examples of authority. They know there are many rational and sensible reasons to question authority. They know that power offers enticements for abuse.

Authoritarian Atheists (A)

These are people who have selectively rejected religious authority because religious authority is fraudulent, intensely corrupt and spews lie after lie, and yet, the Authoritarian Atheist then goes on to embrace other highly similar kinds of authority, and often the worst instances of them. A lying and corrupt government, lying and corrupt media, lying and corrupt academics, and lying and corrupt political parties, which even a child can see have the same disgusting characteristics as religious authority do not raise a red flag for the Authoritarian Atheists. Illegitimate authorities lie and cheat and abuse people while clinging to power, but that is OK because they don't use religion to do it. Thus the Authoritarian Atheist is a fake rebel, changing one master for another but still a slave.

Identity-Atheists (I)

This is an atheist who unfortunately supports bogus religious authority because that authority is tied to their ethnic group. This condition is most common among Zionist atheists. He or she has embraced identity politics, which is a 1970's term meaning a craven clinging to one's ethnic or gender group, in the hope that doing so will lead to political advances and not to what it actually leads to i.e. self-marginalization, abuses against other groups, and corruption.

By education

All atheists are, in my experience, by default what I called Consumerist Atheists. By this I mean they simply don't buy religions' myths and claims. Even the least educated person can be this type of atheist. Two types of education raise an atheist above this level: science and logic. If you have both, you could be called a Consummate Atheist.

Scientific Atheists (S)

Those of us who have gotten around to studying biology and evolution, and therefore have a grounding in the mechanisms of life, gain an understanding of how the emergence of life, though precious, is inevitable due to the nature of the underlying biochemistry. No hand of god is needed. Likewise the mechanisms of evolution can be readily observed on a daily basis and even simulated on computers, without any divine interventions. Every year science gains more and more ground in explaining life and the world while religions lose ground.

Logical Atheists (O)

Those atheists who have yet to study the underlying mechanisms of life may take the view that they know there are no gods because religious argumentation always collapses when analyzed logically. For instance, when one considers the idea that there must be a creator for everything (the First Cause claim), thinking about it one almost immediately wonders: OK, so who created the gods? If an exception is made for them then the First Cause claim collapses.
Thus without scientific grounding Logical Atheist) can nevertheless be satisfied with logical analysis and other critical analyses of religion.

Consummate Atheists (U)

These atheists are both grounded in science and insistent on the use of logic.

Consumerist Atheists (C)

An atheist who takes a practical stance as a consumerist, because simply from the point of view of an information consumer, religion is a very hard sell to anybody whose intellectual capacity is better than that of a child. There is simply no evidence for the gods, so why believe any of that religious horseshit?

The Consumerist Atheist responds to religiosity with lucid pragmatism from different angles:

Obvious scam

An invisible man in the sky? A prophet (con man) who claimed to talk to the invisible man? Utterly ridiculous. Who falls for such nonsense, other than children? Who respects such beliefs, except fools, cowards and the religious con-men themselves? Religion is obviously a scam to obtain power and money. Extraordinary claims require extraordinary proof and there is none.

Waste of time

There is obviously no proof of any gods. Religions are a non-starter. Don't waste your time with their nonsense. Would you buy a bridge if you had no proof that it exists? Religious people, prove your wild claims scientifically or stop wasting my time.
My time is worth something and I won't waste it on something founded on baseless claims.
If there is a god: Let him show himself right now to settle the argument. He never does.

Believers are abusers

Bigots, tribalists and trashy people clearly use religion to justify every form of discrimination and bullying that they want, to perpetuate to satisfy their devilish malevolence. Is there seriously any other practical use for religion except to justify bigotry and abuses? The claims about religion fostering love are a scam: Religion only fosters love for like-minded believers, typically members of a sect, but toward everyone else it encourages stupefying hatred or the scammer's malice.

Unbelievability due to wild claims

The myths used by religion are wild, even zany and often contradict one another. These are just as fanciful stories for kids. Jesus walked on water? That's 2000 year old science fiction. The allah-god talked to Mohammed? That's the schizophrenic ravings of a madman. The bible claims Abraham lived to 175. How plausible is that? Not at all. Extraordinary claims require extraordinary proof.

Unbelievability due to obvious fraud

Myths are clearly recycled. The scammers learn each others' tricks. Prime example: The Jesus life story appears to be stolen from the life of Krishna.
Both were born of a virgin with a god for a father.
Both were crucified and brought back to life.
Both were born on December 25th.
It is as though Jesus was a con man who learned his stories while traveling and then told them to peasants back home.

Counting the combinations

So given these four fulchrums of upbringing, scope, consistency and education, how many types of atheist would there be?

Conclusion

It helps to classify atheists for two reasons.

First, because you need to think about where they are coming from when they claim to be more rational than other people. The sad fact is that not all atheists are rational; many grow up as believers and old habits die hard. Even growing up without religion does not ensure rationality.

Second, because some who self-identify as atheists are hardly atheists at all because they lack training in biology or experience with everyday critical thinking, or fail to see the psychological roots of religiousness don't disappear just because you pull out the weed that is religion.