[An old note that I feel deserved to be posted]
Oftentimes I see atheism and agnostism get confused in meaning and intent, causing individuals to feel overly cautious when using these words to identify themselves. It is important that the semantics are fully clarified, rather than give the illusion that the atheist label is being improperly used. Being precise in definition is essential in establishing a cohesive rebuttal to the religious right, which has dangerously been very active.
Atheism by definition is the lack, or absence of belief in god(s).
Agnosticism is the position that we simply do not know.
Here lies the major difference; while skepticism shows one has a healthy respect for reason, one should not obscure the potentiality of something being true by giving the two possibilities unjustifiable equal weight. Based on empirical evidence and the scientific burden of proof doctrine, you make the assumption something does not exist because there is little rational reason to believe otherwise since there no evidence supporting the opposing view. Falling into the fallacy of giving a proposition with no evidence the same weight and value as a proposition with evidence is a distortion of facts.
If you bring this to its logical conclusion regarding atheism you reach the same outcome; you should not give the existence of God the same weight as its nonexistence, because there is not equal measure, or evidence, on both sides. The standard position of a skeptic is that something doesn’t exist until proven otherwise, especially in the realm of scientific inquiry. Oftentimes, this is ignored to perpetuate and excuse the necessary validation of our beliefs.
You would be essentially an “atheist,” in the more vague general term, toward many positions you deem to be factually lacking because you make an assumption and live you life based on that fact that it isn’t true. It would be silly to keep oneself purely “agnostic” in that position, because you would need equal reasoning for that object existing and it not existing to be a true agnostic; you would need equal weight of reason on both sides. You don’t know if that object exists but you assume, or believe, it does not making you an agnostic-atheist.
Thomas Henry Huxley first coined the term agnostic as “not a creed, but a method,” although it has now become something of a weasel word in the modern context. The definition of one’s own agnosticism is vital to its usage and clarity, because the term on its own is essentially meaningless. An agonistic-atheist would be the most complete phrasing when clarifying one’s lack of belief in a deity. It presents that the individual does not believe, but has not ruled out that deity might exist, regardless of how unlikely. Disowning this possibility is as a poor suspension of reason equal to being certain there is a deity (i.e. theism).
Simply said, agnosticism answers the question of “is there a _____” where ‘I don’t know’ is a completely valid answer, since it addresses a question of certainty. Atheism fundamentally answers a different question of “do you believe in ____” in which the answer is yes or no, simply. There is little room for uncertainty; if you live your life as if it exists, you believe. If you don’t, then the contrary applies.