What does it mean to say that a religion is true, or that it is false? The question is not as easy as it appears at first sight. Bertrand Russell, in Why I Am Not a Christian, runs up against this difficulty. In order to explain why he is not a Christian, he has to know what it means to be a Christian in the first place:

As your Chairman has told you, the subject about which I am going to speak to you tonight is “Why I Am Not a Christian.” Perhaps it would be as well, first of all, to try to make out what one means by the word Christian. It is used these days in a very loose sense by a great many people. Some people mean no more by it than a person who attempts to live a good life. In that sense I suppose there would be Christians in all sects and creeds; but I do not think that that is the proper sense of the word, if only because it would imply that all the people who are not Christians — all the Buddhists, Confucians, Mohammedans, and so on — are not trying to live a good life. I do not mean by a Christian any person who tries to live decently according to his lights. I think that you must have a certain amount of definite belief before you have a right to call yourself a Christian. The word does not have quite such a full-blooded meaning now as it had in the times of St. Augustine and St. Thomas Aquinas. In those days, if a man said that he was a Christian it was known what he meant. You accepted a whole collection of creeds which were set out with great precision, and every single syllable of those creeds you believed with the whole strength of your convictions.

Nowadays it is not quite that. We have to be a little more vague in our meaning of Christianity. I think, however, that there are two different items which are quite essential to anybody calling himself a Christian. The first is one of a dogmatic nature — namely, that you must believe in God and immortality. If you do not believe in those two things, I do not think that you can properly call yourself a Christian. Then, further than that, as the name implies, you must have some kind of belief about Christ. The Mohammedans, for instance, also believe in God and in immortality, and yet they would not call themselves Christians. I think you must have at the very lowest the belief that Christ was, if not divine, at least the best and wisest of men. If you are not going to believe that much about Christ, I do not think you have any right to call yourself a Christian.

Thus Russell reduces being a Christian to believing in God, in the immortality of the soul, and that Christ was at least the best and wisest of men. Of course there are people who call themselves Christians who do not believe one or more of these things, and do not accept that you cannot call yourself a Christian without them. And other people might well give a different list. Thus for example St. Paul has his own requirements:

Now if Christ is proclaimed as raised from the dead, how can some of you say there is no resurrection of the dead? If there is no resurrection of the dead, then Christ has not been raised; and if Christ has not been raised, then our proclamation has been in vain and your faith has been in vain. We are even found to be misrepresenting God, because we testified of God that he raised Christ—whom he did not raise if it is true that the dead are not raised. For if the dead are not raised, then Christ has not been raised. If Christ has not been raised, your faith is futile and you are still in your sins. Then those also who have died in Christ have perished. If for this life only we have hoped in Christ, we are of all people most to be pitied.

Thus St. Paul says that belief in the resurrection of Christ, and therefore in a general resurrection, is required. Otherwise “your faith has been in vain,” which would certainly seem to say that your religion is not true.

Of course, St. Paul is polemically exaggerating the consequences of the position of his opponents. In the first place someone could believe in the resurrection of Christ without believing in a general resurrection. Likewise, even if Christ did not rise from the dead, it does not follow of necessity that anyone’s faith would be entirely vain, but that it would be vain in some respect, since he would still profit from it in various ways, such as by belonging to a Christian community. Similarly, even if Christians have a false belief in the immortality of the soul, there would still be more pitiable people in the world.

We can learn from these two examples. Russell says that you cannot “properly call yourself a Christian,” if you do not accept his list of three beliefs, while St. Paul says that “your faith is in vain” if you do not believe that Christ is risen. There is something common to the two. Some basic belief or beliefs are proposed, such that without these beliefs, it is not worthwhile to count yourself as a believer at all. For St. Paul, this has the form of saying that you should not bother to put your faith in Christ, while for Russell, this has the form of saying that you should not call yourself a Christian.

The basic difficulty is caused by the fact that being a Christian, considered in itself, is not a belief, but membership in a Christian community. Thus saying that “Christianity is true,” or that “Christianity is false,” ought to mean “belonging to a Christian community is true,” or that “belonging to a Christian community is false,” both of which are evidently absurd, since belonging to a community is not the kind of thing which is true or false. But since a Christian community happens to be a community of believers, we identify Christianity as a belief by saying that it is what that community believes.

But the problem is not resolved by this identification, for “what the Christian community believes” is somewhat indeterminate, since Christians believe different things. Russell and St. Paul resolve the issue in similar ways. Russell does so by saying that you cannot “properly call yourself a Christian,” unless you believe certain things, presumably because it is wrong to deceive people about your beliefs. St. Paul does so by saying that your faith is in vain if you think that Christ did not rise from the dead, presumably meaning that it is pointless for you to belong to a Christian community.

Thus both of them are saying that unless you think that such and such is true, it is a bad idea to be a Christian, that is, to belong to a Christian community.

With this analysis we can say in general what it means to say that a certain religion is true, or that it is false. If I say that Mormonism is true, I mean that there are certain true things usually believed by Mormons, which make it worthwhile to belong to a Mormon community, given that I accept those things. Likewise, if I say that Mormonism is false, I mean that there are things believed by Mormons that would make it worthwhile to be a Mormon, if they were true, but in fact those things are false, and consequently it is not worthwhile to be a Mormon. Or more directly, I mean that there are certain things normally believed by Mormons which happen to be false, and the fact that Mormons normally believe these false things, makes it not worthwhile for me to be a Mormon.

Someone might object that this leads to relativism, since according to this analysis, it seems that a religion might be true for one person, but false for another. For example, in an interview conducted by Sergiu Hart, Robert Aumann, the author of the agreement theorem we discussed earlier, explains, among other things, why he accepts Judaism:

H [Sergiu Hart]: So that’s the Center for Rationality. I know this doesn’t belong, but I’ll ask it here. You are a deeply religious man. How does it fit in with a rational view of the world? How do you fit together science and religion?

A [Robert Aumann]: As you say, it really doesn’t belong here, but I’ll respond anyway. Before responding directly, let me say that the scientific view of the world is really just in our minds. When you look at it carefully, it is not something that is out there in the real world. For example, take the statement “the earth is round.” It sounds like a very simple statement that is either true or false. Either the earth is round or it isn’t; maybe it is square, or elliptical, or whatever. But when you come to think of it, it is a very complex statement. What does roundness mean? Roundness means that there is a point, the “center” of the earth, such that any point on the surface of the earth is at the same distance from that center as any other point on the surface of the earth. Now that already sounds a little complex. But the complexity only begins there. What exactly do we mean by equal distance? For that you need the concept of a distance between two points. The concept of distance between two points is something that is fairly complex even if we are talking about a ball that we can hold in our hands; it involves taking a ruler and measuring the distance between two points. But when we are talking about the earth, it is even more complex, because there is no way that we are going to measure the distance between the center of the earth and the surface of the earth with a ruler. One problem is that we canít get to the center. Even if we could find it we wouldn’t be able to get there. We certainly wouldn’t be able to find a ruler that is big enough. So we have to use some kind of complex theory in order to give that a practical meaning. Even when we have four points and we say the distance from A to B is the same as the distance from C to D, that is fairly complex already. Maybe the ruler changes. We are using a whole big theory, a whole big collection of ideas, in order to give meaning to this very, very simple statement that the earth is round.

Don’t get me wrong. We all agree that the earth is round. What I am saying is that the roundness of the earth is a concept that is in our minds. It’s a product of a very complex set of ideas, and ideas are in people’s minds. So the way I think of science, and even of fairly simple things, is as being in our minds; all the more so for things like gravitation, the energy that is emitted by a star, or even the concept of a “species.” Yes, we are both members of the species homo sapiens. What does that mean? Obviously we are different. My beard is much longer than yours. What exactly does species mean? What exactly does it even mean to say “Bob Aumann” is sitting here? Is it the same Bob Aumann as five minutes ago? These are very complex ideas. Identity, all those things that we think of trivially on a day-to-day basis, are really complex ideas that are in our minds; they are not really out there. Science is built to satisfy certain needs in our minds. It describes us. It does have a relationship with the real world, but this relationship is very, very complex.

Having said that, I’ll get to your question. Religion is very different from science. The main part of religion is not about the way that we model the real world. I am purposely using the word “model.” Religion is an experience, mainly an emotional and aesthetic one. It is not about whether the earth is 5,765 years old. When you play the piano, when you climb a mountain, does this contradict your scientific endeavors? Obviously not. The two things are almost, though not quite, orthogonal. Hiking, skiing, dancing, bringing up your children; you do all kinds of things that are almost orthogonal to your scientific endeavor. That’s the case with religion also. It doesn’t contradict; it is orthogonal. Belief is an important part of religion, certainly; but in science we have certain ways of thinking about the world, and in religion we have different ways of thinking about the world. Those two things coexist side by side without conflict.

…

Well, it is your way of putting it. Let me enlarge on it. The observance of the Sabbath is extremely beautiful, and is impossible without being religious. It is not even a question of improving society; it is about improving one’s own quality of life. For example, let’s say I’m taking a trip a couple of hours after the Sabbath. Any other person would spend the day packing, going to the office, making final arrangements, final phone calls, this and that. For me it’s out of the question. I do it on Friday. The Sabbath is there. The world stops.

…

In short, you can be a moral person, but morals are often equivocal. In the eighties, copying software was considered moral by many people. The point I am making is that religion, at least my religion, is a sort of force, a way of making a commitment to conduct yourself in a certain way, which is good for the individual and good for society.

In the first part, Aumann is basically saying that science gives an idealized and approximate description of the world, rather than an exact description. In the second part he attempts to explain why he accepts Judaism, and he seems to be saying that it has little to do with the way the world is, and more to do with what is good for people. In other words, to explain it in the way we analyzed the truth of a religion, “Judaism is true” for Aumann because he believes that it is true that it is good and beautiful to observe the Sabbath, true that it is good to refrain from breaking copyright laws, and so on. And since these things are true it is worthwhile for him to be a member of a Jewish religious community.

You may or may not agree that the Sabbath is beautiful, and you may or may not agree that it is good to refrain from breaking copyright laws. But even if you do agree with these things, you probably don’t conclude that it is worthwhile for you to convert to Judaism. At the same time, you may realize that these things might well make it worthwhile for Robert Aumann to remain a Jew.

Thus our explanation seems to lead to relativism, because Judaism can be true for Aumann, but false for other people. However, there are several problems with calling this result relativism.

First of all, there was some remaining ambiguity in the way we defined the truth or falsity of a religion. Jews might normally believe certain true things, and given that Robert Aumann accepts those things, it might be worthwhile for him to remain a Jew. But it is possible that Jews also normally believe certain false things, such that if Aumann knew they were false, it would no longer be worthwhile for him to remain a Jew. Thus, for example, a Christian would argue that Jews falsely believe that Christ is not the Messiah, and that if Aumann knew that this was false, it would no longer be worthwhile for him to remain a Jew, but to convert to Christianity.

Thus we could make our definition more precise by saying that a religion is true if it is worthwhile to belong to that religion even after you know the truth or falsity of all the beliefs that the members of the religion usually hold, and that it is worthwhile by reason of some of the true things that they hold.

However, this does not sufficiently answer the charge of relativism, because it would still be possible that one religion would be true for one person, and not true for another person.

For example, suppose that theism is true, but that no divine revelation has been given. If Aumann realizes this, he might reasonably believe that it is worthwhile for him to remain a Jew, and unreasonable to convert to Islam, even after knowing the truth or falsity of every concrete belief held by Jews and Muslims. Likewise, a Muslim, knowing the same things, might reasonably believe that it is worthwhile for him to remain a Muslim, and unreasonable to convert to Judaism, even after knowing the truth or falsity of every concrete belief held by Muslims and Jews.

The answer in this case is that the situation simply does not imply relativism, because Aumann and the Muslim do not disagree about anything. Aumann may say, “Judaism is true,” and the Muslim may say, “Islam is true,” but when they explain what they mean and why they say it, they do not disagree with each other about any objective fact. This is no more relativism than it is relativism to admit that one person may prefer vanilla ice cream, and another person chocolate.

Thus, it is possible to mean something reasonable when saying that some religion is true, or that some religion is false. But in the end perhaps it would be better to avoid all the confusion in the first place, by following Robert Aumann’s example and simply distinguishing the question, “What is the world like?” from the question, “Is it, or would it be, good for me to belong to this community of believers?” Of course the answers to these questions are going to be related in various ways, but they are different questions.