Answer by Jim Ashby:
Thanks for the A2A,! I actually have a lot I want to say in my answer.
Here's how dictionary.com defines atheism:
1. the doctrine or belief that there is no God.
2. disbelief in the existence of a supreme being or beings.
The first definition is expressed in the affirmative (belief). The second definition is expressed in the negative (disbelief). Belief in no gods is the same as disbelief in gods. There's no difference.
Atheism is all about (dis)belief. Here's the definition for belief:
1. something ; an opinion or conviction: a belief that the earth is flat.
2. confidence in the truth or existence of something not immediately susceptible to rigorous proof: a statement unworthy of belief.
3. confidence; faith; trust: a child's belief in his parents.
4. a religious tenet or tenets; religious creed or faith: the Christian belief.
A belief is an opinion or conviction (strongly held opinion). Belief, opinion, conviction: these are all subjective concepts. So 'true' atheists do NOT make any objective claims about gods . . . that's what agnostics are for.
1. a person who holds that the existence of the ultimate cause, as God,and the essential nature of things are unknown and unknowable, or that human knowledge is limited to experience.
2. a person who denies or doubts the possibility of ultimate knowledge insome area of study.
3. a person who holds neither of two opposing positions on a topic: Socrates was an agnostic on the subject of immortality.
Whereas atheism is all about (dis)belief; agnosticism, as the definition clearly spells out, is all about knowledge. The words used in definitions #1 and #2 of the word, 'agnostic', are objective words: unknown, unknowable, knowledge, experience. Agnosticism is an objectively realistic stance on the existence of gods. Atheism is a subjectively realistic stance on the existence of gods.
It needs pointing out that definition #3, 'a person who holds neither of two opposing positions on a topic', describes people who are undecided or neutral about the existence of gods. 'Neutrality' implies a CHOICE to not take a stance . . . while 'indecision' suggests that the person really doesn't know (for whatever reason) what to think about the existence of gods.
Of these two stances (neutrality and indecision), neutrality necessarily conflates objective knowledge with subjective belief. What is it that neutrality avoids taking a stance about? BELIEF, of course. If the stance were about knowledge, then it would fit the primary definition and neutrality would be irrelevant. The claim of neutrality violates rational integrity by conflating the objective with the subjective. People sense the equivocation inherent in this timid version of agnosticism and often (rightly) think that 'neutral agnostics' are 'sitting on the fence'.
Sorry, but those last two paragraphs were necessary to deal with a meaning of agnosticism that too many people (both theists and atheists) view as the only meaning. That version of agnosticism does not apply to most agnostics here on Quora: agnostic atheists.
Atheism and agnosticism are two sides of the same freethought coin. One side is subjective: the other side is objective. Both sides are rational and reasonable. Most atheists are, more accurately, agnostic atheists. They value honesty and shun certainty.
But, thus far, I've focused on the nonbelievers and have ignored the believers. The main difference between theists and atheists in public forums is that the vast majority of theists won't admit the possibility there is no God. They have faith. In contrast, atheists readily admit there might be a God. Their belief is provisional (upon evidence). They repeatedly remind theists of the provisional nature of their belief when theists try to paint atheism as a faith. That's a lame-ass false equivalency that theists desperately want to foist upon atheists. Sorry, theists, but faith is what most distinguishes theists from atheists. Having faith means having a closed mind: belief without (and despite the lack of) objective reason.
Most theists are gnostic theists, not agnostic theists. There appears to be very few theists — gnostic or agnostic — who don't feel the need to defend their faith and, indeed, who can even recognize that the phrase, 'defend their faith', is an oxymoron. Faith is belief despite objective reason: it can't be defended. Those who do attempt to defend faith are taking a gnostic position; a claim of subjective knowledge. An intangible knowledge, in the heart and soul, as opposed to objective knowledge from the world around us. This special 'knowledge of faith' conflates the subjective with the objective. It's a fundamental category error . . . another oxymoron. The faithful can't point to anything external to confirm their 'special' knowledge, so the only place left for the 'knowledge of faith' is (where else?) within. The 'special' knowledge of faith is impervious to reason because it's not based on reason. That's why we say: 'If you could reason with religious people, there would be no religious people.'