Here are a few ways of defending Theism against e.g. the evidential problem of evil that don't work (which is not to say there aren't better responses, of course).
“I may not be able to prove there is a God, but no one can prove that there isn’t.”
When presented with a rational challenge to their belief, Theists sometimes say, ‘Look, I cannot prove there is a God; but then it is not possible to prove that there isn’t. So Theism and atheism are both “faith positions”. But then it follows that they are equally reasonable or unreasonable.’
But what, exactly, does ‘prove’ mean here? Prove beyond all possible doubt? It may well be true that we cannot prove beyond all possible doubt that there is no God. But then we cannot prove beyond all possible doubt that there are no fairies or unicorns or Santa. It’s just possible these things exist (perhaps there has been a huge and elaborate CIA-led conspiracy to hide the truth from us). But of course, no one insists that belief in the non-existence of Santa is, then, a ‘faith’ position. Certainly, it does not follow that belief in Santa is just as reasonable as belief that there is no Santa.
Perhaps the suggestion is that it is not possible to prove beyond reasonable doubt that God does or does not exist? But that is a very contentious suggestion. Actually, many Theists believe that the existence of God can be established beyond reasonable doubt. And almost everyone accepts that the available evidence establishes beyond reasonable doubt that there is no evil god. But surely, anyone who acknowledges that ought, then, to acknowledge at least the possibility of there being evidence sufficient to establish beyond reasonable doubt that there is no good God either.
“So how do atheists explain…?”
If we reject belief in God, how do we respond to one of the questions with which we began chapter two – why does the universe exist? What is our answer? Personally, I am not at all sure about how to answer this question. This is a deep and baffling puzzle to which I am not confident I possess a satisfactory solution.
Some Theists may take this to be an astonishing admission: “If you do not know the answer, they you do not know that our answer is incorrect! Your view is no less a faith position than ours.”
But to admit that one does not know the answer to a question is not to say that certain answers cannot reasonably be ruled out. Suppose Sherlock Holmes is having a bad day. There’s been a terrible murder. There are hundreds of suspects. And Holmes just can’t figure out who dunnit. However, while Holmes can’t identify who the culprit is, he is quite sure that certain people are innocent. The butler, in particular, has a cast-iron alibi. So Holmes is justifiably confident the butler didn’t do it, despite the fact that he doesn’t know who did.
In the same way, atheists can admit that there is a mystery about why the universe exists, and that they are utterly baffled by it, while nevertheless insisting that there’s overwhelming evidence that, however it came to be, it certainly wasn’t created by the all-powerful, all-knowing, all-good God of Christian theology. It may be that they can be as justifiably confident of that as they can be that it is not the creation of an all-powerful, all-evil god. Which is something almost all of us are rightly confident about.
An atheist “leap of faith”?
But don’t we all have to make a “leap of faith” at some point – atheists included? Atheists, after all, believe they inhabit a physical world filled with trees, houses, mountains and people. But they believe this only because that is the kind of world their senses appear to reveal. So how can they know their senses are a reliable guide to the truth? How can they know that their experiences are produced by a real world, rather than, say, a supercomputer generating a sophisticated virtual reality, as in the film The Matrix? After all, everything would seem exactly the same, either way. So atheists cannot justify their belief that their senses are fairly reliable. Their belief that the world they seem to experience is real involves a huge leap of faith.
Now it seems to many Theists that they directly experience God. So why shouldn’t they place their trust in this God experience, in the same way atheists place their trust in their perceptual experiences? Neither, it seems can justify their beliefs based on these experiences. Yet we do not normally consider the atheist’s trust in the reliability of his or her senses to be unreasonable. But then why should we consider the theist’s trust in the reliability of his or her religious experiences to be any less reasonable?
Further, the Theist might claim that, precisely because they do place their faith in their God experience, they don’t then have to place any additional faith in the reliability of their normal perceptual experiences. If there is a benevolent God of the sort the Theist seems to experience, that God will not allow them to be systematically deceived by their senses. So trusting their senses does not require a further leap of faith.
So, the Theist may conclude, at least for someone who has such religious experiences, belief in God need be no more or less a faith position than is the atheist’s belief in the external world.
This is an ingenious line of argument. It may contain some truth. It might be true that atheism is a faith position because any belief one holds about how things stand outside of ones own mind is ultimately a faith position (though I have my doubts even about this – for example, some philosophers argue that the view that physical objects, other people, etc. exist outside my own mind is the best available explanation I possess for various perceptual experiences I have, and is thus not a faith position at all, but a well-confirmed hypothesis).
However, even if any belief about how things stand outside ones own mind requires a leap of faith, it does not follow that it is as reasonable for Theists to place their trust in their God experiences as it is for atheists to trust their normal perceptual experiences.
Here’s one obvious difficulty with the suggestion that trusting a supposed experience of God involves no greater leap of faith than trusting the deliverances of your other senses.
Observation reveals that people have a very diverse range religious experiences. Some believe that, through such experiences, they know that there are many gods, some one god, and some (such as some Buddhists) no gods at all. Some experience the Judeo-Christian God, others Thor, others Zeus, others Mithras, so on. People have experienced literally thousands of gods and other supernatural beings (saints, angels, ancestors, etc.), beings with a huge and diverse range of characteristics. The existence of any one of these gods typically rules out the existence of many, and in some cases all, of the others. So we know that at least many of these experiences must be at least in large part delusory. But then isn’t someone who, knowing all this, nevertheless insists that their own particular religious experience is a reliable indicator of the truth being excessively credulous – far more credulous than someone who merely takes their normal sensory experiences to be fairly reliable (for at least our normal senses don’t provide us with good evidence that they are not themselves fairly reliable)?
A second difficulty with the above suggestion is that while the Theist’s assumption that they experience God might then lead them to trust the deliverances of their other senses, their other senses then quickly furnish them with ample evidence that there is no such benevolent being (see the problem of evil above). So, unlike the assumption that our normal senses are pretty reliable, the Theistic assumption actually ends up undermining itself.
N.B. This is from my OUP Very Short Intro to Humanism. Also note that the final section, while addressing the objection based on skepticism about the external world, would apply equally to the "atheism is a faith position too" move based on skepticism about logic (i.e. the point that logic cannot be justified in a non-circular manner). I'll leave you to figure out exactly how...