Here is a famous passage from Bertrand Russell's Is There a God?
Many orthodox people speak as though it were the business of sceptics to disprove received dogmas rather than of dogmatists to prove them. This is, of course, a mistake. If I were to suggest that between the Earth and Mars there is a china teapot revolving about the sun in an elliptical orbit, nobody would be able to disprove my assertion provided I were careful to add that the teapot is too small to be revealed even by our most powerful telescopes. But if I were to go on to say that, since my assertion cannot be disproved, it is intolerable presumption on the part of human reason to doubt it, I should rightly be thought to be talking nonsense. If, however, the existence of such a teapot were affirmed in ancient books, taught as the sacred truth every Sunday, and instilled into the minds of children at school, hesitation to believe in its existence would become a mark of eccentricity and entitle the doubter to the attentions of the psychiatrist in an enlightened age or of the Inquisitor in an earlier time.
So far, so good. Russell is of course doing more than underscoring a couple of obvious points in the theory of argumentation. He is applying his points of logic to the God question. Here too I have no complaint. If the existence of God has not been disproven, it does not follow that God exists or even that it is reasonable to believe that God exists.
But the real appeal to atheists and agnostics of the Teapot passage rests on a third move Russell makes. He is clearly suggesting that belief in God (i.e., belief that God exists) is epistemically on a par with believing in a celestial teapot. Just as we have no reason to believe in celestial teapots, irate lunar unicorns (lunicorns?), flying spaghetti monsters, and the like, we have no reason to believe in God. But perhaps we should distinguish between a strong and a weak reading of Russell's suggestion:
S. Just as we cannot have any reason to believe that an empirically undetectable celestial teapot exists, we cannot have any reason to believe that God exists.
W. Just as we do not have any reason to believe that a celestial teapot exists, we do not have any reason to believe that God exists.
Now it seems to me that both (S) and (W) are plainly false: we have all sorts of reasons for believing that God exists. Here Alvin Plantinga sketches about two dozen theistic arguments. Atheists will not find them compelling, of course, but that is irrelevant. The issue is whether a reasoned case can be made for theism, and the answer is in the affirmative. Belief in God and in Russell's teapot are therefore not on a par since there are no empirical or theoretical reasons for believing in his teapot.
Another suggestion embedded in the Russell passage is the notion that if God existed, he would be just another physical thing in the physical universe. But of course this has nothing to do with anything maintained by any sophisticated theist. God is a purely spiritual being.
Another problem with the teapot analogy is that God as traditionally conceived in the West is not an isolani — to use a chess expression. He is not like an isolated pawn, unsupported and unsupporting. For if God exists, then God is the cause of the existence of every contingent being, and indeed, of every being distinct from himself. This is not true of lunar unicorns and celestial teapots. If there is a lunar unicorn, then this is just one more isolated fact about the universe. But if God exists, then everything is unified by this fact: everything has the ground of its being and its intelligibility in the creative activity of this one paradigmatic being.
This is connected with the fact that one can argue from general facts about the universe to the existence of God, but not from such facts to the existence of lunar unicorns and celestial teapots. Thus there are various sorts of cosmological argument that proceed a contingentia mundi to a ground of contingent beings. But there is no similar a posteriori argument to a celestial teapot. There are also arguments from truth, from consciousness, from apparent design, from desire, from morality, and others besides.
The very existence of these arguments shows two things. First, since they move from very general facts (the existence of contingent beings, the existence of truth) to the existence of a source of these general facts, they show that God is not a being among beings, not something in addition to what is ordinarily taken to exist. Second, these arguments give positive reason for believing in the existence of God. Are they compelling? No, but then no argument for any substantive philosophical conclusion is compelling.
People like Russell, Dawkins, and Dennett who compare God to a celestial teapot betray by so doing a failure to understand, and engage, the very sense of the theist's assertions. To sum up. (i) God is not a gratuitous posit in that there are many detailed arguments for the existence of God; (ii) God is not a physical being; (iii) God is not a being who simply exists alongside other beings. In all three respects, God is quite unlike a celestial teapot, a lunar uncorn, an invisible hippopotamus, and suchlike concoctions.
I am quite at a loss to explain why anyone should think the Teapot analogy any good. It leaks like a sieve.