Let's start things off with his quote of Russell:
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.
Vallicella first acknowledges the obvious points that just because there is no evidence A does not exist, we can not conclude A exists. However, he then seems to go into a third point that strikes me as not only being irrelevant to Russell's main point, but also completely avoids Russell's actual third point: belief in God, or the magic teapot, is not sustained based upon the evidence, but upon the inherited traditions and the tremendous amount of social pressure to be a believer. The number of believers who come to believe in God because of arguments like the Cosmological argument is very small, indeed. However, instead of addressing this point of Russell, Vallicella takes a turn which seems to take the analogy and discard it because Russell's teapot doesn't have a history of belief.
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.
Sticking with Russell's teapot for the moment, why don't we have any reason to believe it exists? I'm drinking tea right now, and typically drink 2-4 quarts of iced tea each day. On the days where I don't drink it, I get headaches. I can certainly interpret that as a the divine retribution of Russell's teapot to my failure to offer an appropriate worship for the day.
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.
Vallicella does not provide a reason for making this distinction. It's just as well, because (S) is not a valid interpretation of Russell's proposition. Unlike the teapot, any putative omnipotent God certainly could offer us any manner of reasons to accept Their existence, of essentially any possible level of reliability. Of course, that such proof has not been offered is not proof of Their non-existence, but that is very different from saying we can not have proof.
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.
This is an interesting standard of evidence: it doesn't matter if the arguments are compelling or not, they just have to exist and be made into a reasoned case. It occurs to me that this is not a difficult thing to accomplish for the Russell's teapot (the Teapot); I can make a reasoned case, that almost no one will find compelling, for it's existence. First is the evidence I have already presented, which we might call the Argument from Compulsion: when I stop performing acts of worship to the Teapot, I have physical symptoms. Then there is the Argument from Dominant Language: of all the Western European countries, it is England whose language has become the commercial language of the world, because they are known for drinking tea, and the Teapot has rewarded them for it. I will end this list with the Argument from Antioxidants: the Teapot wishes to encourage our worship, and so has made our worship healthy for us.
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.
Here in the USA, for most theists, their putative God at one time or another had a very physical incarnation, and many of them believe He still has that incarnation. Now, if you are a Jehovah's Witness (JW), or some other sect who believes that Jesus was not God, then you might accept a purely spiritual God (as the JWs do). If Vallicella belonged to such a belief system, I do not believe he would enjoy the positive reputation he has among a variety of Trinitarian bloggers, so I will venture that he does accept some sort of physical part of God at some point in God's existence,and so does not himself believe God is purely spiritual.
Also, there is nothing in Russell's logic or analogy that relies on the Teapot being a physical thing. The analogy works perfectly well with objects that have no physical instantiation, like the Flying Spaghetti Monster (FSM). I am curious how Vallicella can specifically note the FSM earlier in his post, and yet forget here that the FSM meets his criteria here for being 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.
That's a pretty remarkable jump, from simply being a purely spiritual being to being the grounding of the universe. More to the point, it seems to be saying that the analogy is invalid because this putative God has a good story behind it. Perhaps Vallicella is unaware of how easy it is to compose such background stories for the Teapot. For example: the Teapot did create the universe just to put our planet in the perfect position to grow tea and have a species to worship it through drinking that tea. That the universe is perfectly suited for the drinking of tea is all the proof you should need for the Teapot.
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.
That Vallicella fails to see how much these arguments favor to the Teapot jut as much as his putative God seems to be due to some blindness or lack of imagination on the subject.
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.
The interpretation of the evidence to provide inductive support for a putative God fails to account for the lack of specificity: the same arguments can be used to support any such construct, including the Teapot or the FSM.
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
To sum up, each of Vallicella points can be applied equally easily to the Teapot, much less the FSM. His own critique of the argument fails under the weight of the expectations he feels the need to employ for his God.