Religious belief is of course criticized on a variety of fronts. Critics often focus on the truth-claims of religions, such as that a God or gods exist, that Jesus rose from the dead, or that there is an afterlife. They insist these claims are unjustified. Some go further still, arguing that not only is it not reasonable to believe these claims are true, it's reasonable to believe they are all false.

However, there is another much more radical kind of criticism to consider. This more radical sort of critic agrees with the religious naysayer that religious claims are not true. However, they also insist that neither are they false. In fact, according to the more radical critic, a sentence such as ‘God exists’ fails to make any claim at all.

Of course, if someone says ‘God exists’, it looks like they're asserting something capable of being true or false. The theist thinks they assert something true, the strong atheist (who denies that God exists) something false. But, according to the more radical critic, this appearance is deceptive. Someone who says ‘God exists’ doesn't even get as far as asserting something, let alone something true or false. This more radical sort of atheist doesn't say ‘God exists’ makes an unjustified claim, or even a false claim; they say that ‘God exists’ fails to make any claim at all.

The philosopher A. J. Ayer is perhaps the best-known critic of this more radical sort. According to Ayer, ‘God exists’ fails to assert anything at all. But why?

The key to understanding Ayer's criticism is a principle called the Verification Principle:

A statement is verifiable just in case there are either grounds for supposing it is true, or grounds for supposing it is false.

So, for example, the statement:

is verifiable. There are obviously, plenty of grounds for thinking the statement is true. I have myself verified that the statement is true on a trip to France: I saw it with my own eyes. But even if you have not been to Paris, you can still verify the statement in many other ways: by listening to other reliable people who have been to Paris and seen the tower, by checking other reliable resources such as geography books, maps of Paris, Google Earth, and so on.

We can also verify that some statements are false. Take for example:

That this is false this is pretty easily confirmed by various observations.

Even just some evidence – evidence that falls far short of establishing that it is true – is still enough to verify it.

Notice that in order to verify a statement, you only need some grounds for thinking it's true. You don't need proof beyond all possible doubt or even beyond reasonable doubt.

Also notice that the Verification Principle says that in order to be meaningful, a statement must be verifiable. It doesn't actually have to be verified. If there could be an observation that confirms that it's true, or that it's false, then it's verifiable, whether or not any such observation has been or will be made.

In his Language, Truth, and Logic, Ayer signs up to the Verification Principle. He also clarifies two ways in which a statement can be verified. First, a statement can be verified by observation. If there are observations ‘relevant to determining a statement's truth or falsehood’, then it's verifiable. For example, I can verify that the Eiffel Tower is in Paris by going and directly looking at it. Or I can verify that my dog is in the garden if I can hear barking coming from there.

However, there is another way a statement can be verified, according to Ayer: if the statement is true in virtue of meaning. So, for example, the sentence ‘All triangles have three sides’ is true by definition. We need only grasp the meaning of that sentence in order to know that it is true. We don't need to go and observe any triangles. Similarly we can know ‘Not all triangles have three sides’ is false just by understanding what it says. We don't need to go and check any actual triangles. That all triangles have just three sides is something we can know by reflection, from the comfort of our armchairs. Statements that are similarly true in virtue of meaning are called analytic statements.

What about scientific statements such as that electrons exist, or that the Earth goes round the Sun, or that the Earth is many millions of years old? Can these statements be verified?

Yes, they can. Of course that electrons exist is not an analytic statement. It could turn out to be false. But we can verify that electrons exist by observation. Of course, we can't directly observe electrons: they are far too small. But we can observe certain experimental results – results that do confirm that electrons exist. Remember, in order to verify that electrons exist, these experiments don't need to prove that electrons exist. They just need to provide us with some grounds for thinking electrons exist. Similarly, while we can't directly observe that the earth existed millions of years ago, we can observe many things that confirm that the Earth is at least that old, such as sedimentary layers in the rocks beneath our feet and evidence of slow tectonic plate movement taking place over millions of years.

At least some religious statements also appear to be verifiable. For example, that a certain miracle occurred might be confirmed by direct or indirect observation. That God created the entire universe around 6,000 years ago is also a verifiable statement - observation has established it's false. But what about the statement ‘God exists’? It is at this point that Ayer applies his Verification Principle to try to show that ‘God exists’ is meaningless. For according to Ayer, ‘God exists’ is not verifiable. The statement is not analytic. And there is no conceivable observational evidence that could count for or against it. Therefore, says Ayer, ‘God exists’ is meaningless.

Notice that, actually, this is a rather unusual way of using the term ‘meaningless’. After all, we would ordinarily say that plenty of sentences that fail to make a claim are nevertheless ‘meaningful’. ‘The door is shut’ clearly asserts something. But the question ‘Is the door shut?’ and the command ‘Shut the door!’ do not make claims. They don't assert that something is the case. For that reason, they are unverifiable. But we wouldn't ordinarily say they are meaningless. Other expressions, such as ‘Congratulations on becoming a father!’ and ‘Down with the monarchy!’, also fail to make claims, but we would not ordinarily say that these sentences are meaningless. So it's worth remembering that Ayer is using the term ‘meaningless’ in a special way, to mean ‘does not assert anything’ or ‘does not make any claim’.

So, on Ayer's view, ‘God exists’ is not false. Rather, it's meaningless. It looks like a claim is being made, but on closer examination, once we realize the statement is unverifiable, it turns out not to claim anything at all. Of course, religious people who say ‘God exists’ think they are making a hugely important claim, but the truth, according to Ayer, is that ‘God exists’ asserts nothing at all. So Ayer is an atheist of the radical sort.

We have now set out Ayer's criticism of religious claims such as ‘God exists’. Ayer uses the Verification Principle to try to show that they fail to make any claim at all. They are, in that sense, ‘meaningless’.

But is Ayer correct?

I don't think so. I am an atheist, but not of Ayer's radical sort. I think that, certainly in most cases, people use the sentence ’God exists’ to make a claim. I just happen to think that the claim is false.

There are two ways in which you might criticize Ayer's argument. First, you might attack his principle – the Verification Principle. If you can show that the principle is false, or at least unjustified, then his conclusion – that ‘God exists’ fails to make a claim – is unjustified too. Second, you might argue that, whether or not the Verification Principle is a reasonable principle, ‘God exists’ is in fact verifiable. Let's look at each of these criticisms in turn.

The criticism of the Verification Principle that is probably best known is – it's not itself verifiable. Therefore, by its own light, it's meaningless. This is one of the criticisms you may be expected to wheel out if you are answering an exam question on Ayer on religious language, for example.

However, is it true that the Verification Principle is unverifiable? Couldn't there be observations that support, or undermine it? Think about this argument: we start to learn language through observation (which is itself something we can observe). In particular, as youngsters, we learn to associate words with things we can observe in our environment. We hear the word ‘car’ said while our parent points at a car, for example. But doesn't this suggest that the foundations of language are rooted in observation? So perhaps we can, after all, make a case for saying that, when language is entirely detached from any possible observation, it fails to have any meaning? I'm not at all sure that this is a good argument. But it's not an absurd argument. In which case, perhaps we can make a good observation-based case in favour of the Verification Principle? Perhaps we shouldn't just assume that the Verification Principle is unverifiable?

Even if the Verification Principle is not self-condemning in the way it's widely supposed to be, that doesn't mean it's true, or even reasonable. In fact, in Language Truth and Knowledge, Ayer uses the Verification Principle to try to show that ‘God exists’ fails to assert anything while never actually providing any reason to think that the principle is true. So, in that book, Ayer's argument depends on a highly contentious and unjustified principle. But then his conclusion is unjustified too.

Setting aside whether the Verification Principle is true, is it the case that ‘God exists’ is unverifiable?

Some suggest that we can know that God exists just by reflection on what ‘God’ means. If God means ‘greatest conceivable being’ and that in turn requires that that being exist, then it may be analytic that God exists! In which case, that God exists is verifiable. Alternatively, perhaps the very idea of God involves some sort of logical contradiction (a bit like the idea of a four-sided triangle, say, or a non-spatial mountain). If we can show that, then we can verify that ‘God exists’ is false. So it is a verifiable statement.

What about verifying ‘God exists’ by observation – can that be done? Many people believe that there's good observational evidence that God does not exist – evidence provided by for example the depth of suffering we see in the world. If by God we mean a being that is maximally powerful, knowledgeable and good, then there should be no pointless suffering in the universe. Yet there appears to be an extraordinary amount. Isn't this good evidence that that there is no such God?

Others argue that belief in God, if not established conclusively by observation, is at least supported by observation. The fine-tuned character of the universe, for example, is supposed by some to provide us with at least some evidence that it was designed by such a divine architect. In which case not only could there be evidence for God, there is evidence for God.

Ayer's argument is also ambiguous. What, exactly, counts as an observation? The theologian John Hick suggests that ‘God exists’ can be confirmed after we die, potentially – for we may get to meet God (this is what Hick calls an ‘eschatological’ verification). Does Ayer's Verification Principle allow for that sort of verification? Would meeting God in the afterlife count as an ‘observation’? That's not entirely clear.

Ayer's argument for the radical kind of atheism that says that ‘God exists’ is not false but fails to assert anything at all looks, on closer examination, to be a rather miserable failure.