Ok, you are right that I missed the situation of people who say things but fail to live up to them in obvious ways. That is probably simply because I don't really see this in the religious people I am most acquainted with. My guess is that if we leave out people who are actually not telling the truth about what they believe (i.e. people who are literally lying about what they hold), that happens mainly because of akrasia and other similar situations where their desires are in conflict with their explicit beliefs about what they should do, and they follow their desires instead of their belief. If this is right, it wouldn't be necessary to make a distinct category of belief here, just as it isn't necessary to say that I have a "belief in belief" that I should not waste so much time browsing the internet, even if I do it. The desire is a sufficient explanation without having to modify the belief.
About the people virtually certain their religion is false, I should have said "in every way under their control". In other words it is precisely the voluntary aspects that they are choosing to conform to the belief. But there are many involuntary aspects that reveal the contrary estimate. There are also voluntary actions which are somewhat indifferent, where they could consistently do the action if the thing was true, but they might be somewhat more likely to perform that action if they held the contrary internal estimate. For example, since emotional reactions are somewhat involuntary they can manifest something about it; someone with a high internal estimate of his religion is more likely to react badly in an emotional way to someone else leaving the religion, while someone with a low internal estimate is likely to be more calm about it. Likewise, as an example of the voluntary case, if someone says "I realize there is plenty of evidence against my religion," this is a somewhat indifferent voluntary action, since it is consistent with the religion being true, but it is more likely to be said by someone who has the low estimate.
someone with a high internal estimate of his religion is more likely to react badly in an emotional way to someone else leaving the religion, while someone with a low internal estimate is likely to be more calm about it.
I don't think there's reason to believe that.
If someone says something I know to be utterly false I laugh. There needs to be a basis of doubt to feel bad emotionally.
I am not sure that it is productive to tell certain people that they do not really believe what they claim to believe, and that they only believe they believe it. I have an alternative suggestion that could possibly be more useful.
Binary Beliefs
It seems that human beings have two kinds of beliefs: binary beliefs and quasi-Bayesian beliefs. The binary beliefs are what we usually think of as beliefs, simple statements which are true or false like "Two and two make four," "The sun will rise tomorrow," "The Messiah is coming," and so on.
Binary beliefs are basically voluntary. We can choose such beliefs much as we can choose to lift our arms and legs. If I say "the sun will rise tomorrow," I am choosing to say this, just as I can choose to lift my arm. I can even choose the internal factor. I can choose to say to myself, "the sun will rise tomorrow." And I can also choose to say that the sun will NOT rise. I can choose to say this to others, and I can even choose to say it to myself, within my own head.
Of course, it would be reasonable to respond to this by saying that this does not mean that someone can choose to believe that the sun will not rise. Even if he says this to himself, he still does not act as though the sun is not going to rise. He won't start making preparations for a freezing world, for example. The answer to this is that choosing to believe something is more than choosing to say it to oneself and to others. Rather, it is choosing to conform the whole of one's life to the idea that this is true. And someone could indeed choose to believe that the sun will not rise in this sense, if he thought he had a reason to do so. If he did so choose, he would indeed begin to make preparations for a dark world, because he would be choosing to conform his actions to that opinion. And he would do this voluntarily, just as someone can voluntarily lift his arm.
Quasi-Bayesian Beliefs
At the same time, human beings have quasi-Bayesian beliefs. These are true degrees of belief like probabilities, never really becoming absolutely certain of the truth or falsity of anything, but sometimes coming very close. These are internal estimates of the mind, and are basically non-voluntary. Instead of depending on choice, they actually depend on evidence, although they are influenced by other factors as well. A person cannot choose to increase or decrease this estimate, although he can go and look for evidence. On account of the flawed nature of the mind, if someone only looks for confirming evidence and ignores disconfirming evidence, this estimate in principle can go very high even when the objective state of the evidence does not justify this.
Belief in Belief
It seems to me that what we usually call belief in belief basically means that someone holds a binary belief together with a quasi-Bayesian belief which conflicts with it. So he says "The Messiah is coming," saying it to himself and others, and in every way acting as though this is true, even though his internal Bayesian estimate is that after all these thousands of years, the evidence is strongly against this. So he has a positive binary belief while having a very low estimate of the probability of this belief.
The reason why this often happens with religion in particular is that religious beliefs very often do not have huge negative consequences if they are mistaken. In principle, someone can choose to believe that if he jumps from the window of the tenth story of a building, he will be ok. In practice, no one will choose this on account of his non-voluntary Bayesian estimate that he is very likely to be hurt if does so. But a person does not notice much harm from believing the Messiah is coming, and so he can choose to believe it even if his internal estimate says that it is likely to be false.
A cautionary note: one might be tempted to think that religious people in general have belief in belief in this sense, that they all really know that their religions are unlikely to be true. This is not the case. There are plenty of ways to distort the internal estimate, even though one cannot directly choose this estimate. I know many very religious people who clearly have an extremely high internal estimate of the truth of their religion. They REALLY BELIEVE it is true, in the fullest possible sense. But on the other hand I also know others, also extremely devout, who clearly have an internal estimate which is extremely low: they are virtually certain that their religion is false, and yet in every way, externally and internally, they act and think as though it were true.