An intellectual combatant once denigrated his opponent by claiming that the opponent did not even differentiate between atheism and agnosticism. Prima facie, this distinction is obvious; even a fifth grader can understand it. However, the opponent might have downplayed the differences only to focus attention on the similarities between atheistic and agnostic views.
Concerning the “difference” between atheism and agnosticism
Most people recognize the difference between the atheistic and agnostic position. Atheism, they point out, denies the existence of any deity. On the other hand, agnosticism only denies knowledge of a god’s existence, allowing for the possibility that a god might exist.
Accordingly, the agnostic is supposed to “leave open the possibility of a god’s existence; whereas the atheist allegedly shuts the door on that possibility (* See note below). We could imagine the agnostic saying something like this: “We don’t have knowledge of a god, but there could be one. Who knows?” And imagine also the atheist making the strong (loud?) assertion that “there is no god!” On this view, the agnostic is seen as a tentative, uncommitted nonbeliever, a “fence-sitter” (someone who cannot decide until he sees which the way “metaphysical winds” blow); whereas the atheist is depicted as intransigent (even dogmatic?) in his declaration that there is no god.
This is the conventional, man-in-the-street-view of atheism and agnosticism. This is fine for people anxious to get on with the business of living and impatient with nitpicking, philosophical distinctions. But this common-sense picture tends to ignore the important similarities between the atheism and agnosticism. Moreover, the conventional view can result in the type of caricatures noted above.
I shall emphasize the similarity, rather than the difference, between the two “non-believer” positions. Admittedly there are some people who call themselves “agnostic” but retain their belief in a god. A more accurate designation for that view would be “fideist,” or the view that recognizes humans’ lack knowledge but retains faith in a deity. However, the more common form of agnosticism implies a lack of belief in a deity. Like atheism, it rejects belief in a deity. The agnostic philosophy is “a-theistic” insofar as it omits deity. Like atheism, this form of agnosticism expresses a secular approach (to life) devoid of deity.
In this context you will find some people arguing that the correct use of the term “atheist” is to denote a philosophical perspective which is devoid of deity, i.e., “a-theistic” inasmuch as it excludes belief in a god. The argument, then, is that “a-theism,” taken in this sense, does not logically entail the metaphysical, categorical declaration that there is no God. The debate would then focus on the correct meaning of “atheist” and “atheism.” (“Positive atheism” denies existence of deity; “negative atheism” proceeds without reference to deity.)
For now let us bypass this debate over the semantics of “atheism.” We can admit that ordinarily the term “atheist” connotes the denial that a god exists. In this regard the conventional view does not mislead us. (Atheists tend to deny the reality of a deity; agnostics simply omit belief in such ‘reality.’) But let us set aside for now the distinction between the atheistic and the agnostic views. Instead, let us focus on the similarity between them.
Dismiss the notion that the agnostic is really just an uncommitted, “fence-sitter.” Surely many agnostics are not. For such people, agnosticism does not imply a tentative, uncommitted position. Instead it connotes a strong commitment to rationality and the “ethics of inquiry.” Here imagine the agnostic applying W. K. Clifford’s ethical principle that we’re not to believe anything unless we have adequate evidence to support the belief. Accordingly, many agnostics reject belief in a god as neither a rationally nor an ethically justifiable position. This certainly is not the view of a tentative, “fence-sitter.”
Agnostics emphasize belief in a supernatural being is outside the scope of human knowledge, and point out that nobody has ever provided adequate, objective grounds for such belief. In other words, our agnostic doesn’t simply deny knowledge of the existence of a deity. He denies that we have any rational grounds to support belief in a deity. Some agnostics will even say that, with respect to specific “gods” (e.g., the God of Judeo-Christianity) their position is “atheistic” in the strong sense. No such ‘god’ ever existed. Agnostics tend to agree with atheists that all talk of the supernatural and deity is vague, and that the proposition that God exists is far from clear, but even when relatively clear, it is by and large a groundless proposition.
What about the atheist? Well, if he is a rational individual, he does not simply issue the loud declaration: “There is no god.” On the contrary, he will point out that (despite centuries of theologies and apologetics) we lack knowledge of any deity nor anything remotely close to rational grounds for belief in a deity. He might also question the meaning and coherence of propositions which assert that a deity exists and has specifiable properties.
Here the atheist is in full agreement with the agnostic. Both take the rationally-based position which denies any grounds for deity. Their difference seems to be one of emphasis, with one emphasizing that there is no deity because there are no rational grounds for a deity, and the other emphasizing our utter lack of knowledge and compelling evidence for a deity’s existence, and proceeding as if there were none. For all practical purposes, the agnostic “rejects” deity in much the same way as the atheist. He simply is not as emphatic in expressing his rejection.
* In this connection, consider the phrase “possibility of god’s existence.” On the conventional view, the atheist supposedly denies the possibility of god’s existence; whereas the agnostic leaves the door open on this possibility. (Philosophers who defend Christian theism make much of this alleged “possibility of God’s existence.” Likewise, those who argue that science and empirical inquiry cannot disprove the existence of God, also emphasize this notion of the possibility of God’s existence.)
Formalists emphasize possibility as logical possibility. Here ‘the possibility of X’ means ‘X does not entail a contradiction.’ So the possibility of god’s existence means that the proposition ‘god exists’ does not entail a contradiction.
Some philosophers characterize logical possibility in terms of the concept of possible worlds. Here the proposition ‘Possibly X exists’ is translated as ‘There is a possible world, call it “Tangerine” in which X exists,’ without implying that possible world “Tangerine” is the actual world.
But as Daniel Dennett points out (See his Darwin’s Dangerous Idea) there are other kinds of possibilities. We can speak of something being physically possible (or impossible); or biologically possible (or impossible). It is physically impossible that I high jump (without assistance) a twenty-foot high barrier, although it is logically possible (no self contradiction). A biologist will tell us that it is biologically impossible for a virgin to give birth, although the proposition asserting a virgin birth is not a logical contradiction.
Defenders of the theistic view often demand that critics of belief in a deity prove that the existence of such a deity is impossible. Some say that critics have to disprove G’s existence. Obviously, this demands an awful lot. But to even understand their requirement, one should clarify the type of impossibility at issue here. Is it logical impossibility? Then one would have to show that the ‘god-exists’ proposition entails a contradiction. Is the possibility at issue a physical possibility? Probably not, since the deity is supposed to be a spiritual being. The physical possibility would have to apply to the alleged interaction between this spiritual being and the human, material world. Here the skeptic would have a more manageable task, arguing that such interaction is physically impossible.
From the other direction, the theists might be encouraged to find that the skeptic has not proven the impossibility of his god’s existence. But this merely implies that the theist can claim nothing beyond the logical possibility of his god’s existence, which is not a very secure ground on which to stand.
Contrary to philosophers who focus on the issue of possibility or impossibility of deity, scientifically-based writers (including certain philosophers) prefer to state the problem (of existence of deity) in terms the strength or weakness of the case that one can make for existence of a deity. What rational grounds or empirical evidence can be connected (in some way) to the claim that a deity is real? Here the scientific-based skeptic finds that the defenders of theism have not even managed a weak case in support of their “god’s” existence.