In critiques of their books, and in public debates, atheists such as Richard Dawkins seem to often hear statements such as "Sure, we Christians believe in God simply through faith....but you atheists have faith too, faith in there not being a God". If one watches, for example, the debate between Dawkins and Oxford math professor and Christian John Lennox on YouTube, you will hear Lennox make this assertion about half way through the debate. Dawkins vehemently denies it, and I think he is basically correct in doing so.
But this claim about atheists having faith in the nonexistence of a God is heard so often that it seems worthwhile to examine and analyze it in some detail.
Classical logic would hold that if someone, let's call him/her "A", asserts the existence of X, the burden of proof is on A. Here "proof"can simply mean evidence that makes A's assertion plausible, not of course a rigorously logical proof, as these are only possible in formal logic or mathematics.
For example, if I assert that there is an elephant in the next room, you might quite rightly be skeptical unless I can give you some plausible reason as to how I know that, or why I believe that. Of course, to the extent that such a beast would represent a trampling threat, you might well decide to play it safe and act quickly as if it were true by fleeing the scene. This would not be the same as believing the claim of the elephant, and when a safe position is reached you might well ask for what evidence I had for the claim.
The situation between asserting X exists and X does not exist are in general not symmetric in that sense. Our legal system recognizes this with regard to the guilt of a suspect, where the existence of guilt in a defendant is assumed not true unless it is established beyond reasonable doubt by a judge or jury.
Let us digress a little to ask what does faith really mean? I think it is quite complex. There is a cynical definition that it means "believing something that you have no good reason to believe". It is in fact a rather slippery word that is commonly used to mean different things. It seems that in the Bible, for example, it is used not to mean faith that God exists, but rather trusting in God or Jesus doing the right, loving things for us. In other words, it is simply assumed that such beings exist. As we might say of a person, "I have complete faith that Jane will do the right thing---I know her, and she will not let me down".
But it is clear that this meaning of faith cannot be used to justify belief in some being or person actually existing. So Lennox cannot be using Faith in this way when he states in the debate that he believes in God and Jesus on faith. And of course it makes no sense to say something like "Atheists have faith too", when using faith in this sense.
It seems that the term Faith is often used as almost synonymous with hope----that is, if a person asserts that he believes in God on faith, he or she may really be saying that he/she fervently hopes that God exists, and has decided to convince himself that it is true. It must be admitted that an atheist might hold similar hope that God does not exist, so Lennox's claim might be plausible here. (Indeed, regarding the God as described in so much of the Old Testament, I admit to having the hope that such a God does not exist).
I rather understand and admire a definition given by Mr. C. S. Lewis, to the effect that faith is a sort of steadfastness in a position, where one does not allow oneself to be swayed by mere mood swings, once one has in ones best, most rational moments, decided on a position. When defined this way, it can of course be a precept to be followed by agnostics and atheists as well as by theists. In fact, it would seem to be a really a good mental strength to cultivate in any intellectual context. But I must add that I do not think very many people intend this meaning when speaking of their faith.
I think that there is arguably some evidence for theism, however slight, in the sense of the "prosecution" having some exhibits on their behalf (I am going back here to the analogy of a guilty verdict corresponding to the assertion that God exists). Maybe not "good enough" evidence, but not "no evidence". But it is evidence of a subtle nature, and mostly subjective. Indeed, if I did not feel that there was some evidence, I would call myself an atheist rather than an agnostic. Indeed, I think one mistake Lennox made in the debate is that he fails to stress that Christians do have, or believe they have, evidence for their belief. But it is largely subjective.
What is this evidence you might ask? Well, it is the seeming fine tuning of the universe, the awesome subtlety of the universe in terms of physics and life, and the yearning I think we all have to see things eventually be "put right". Of course, as I have argued elsewhere on this blog site, none of these are strong defenses of theism, rather just what might be called "inklings". Not necessarily of Christian theism, but perhaps of some sort of non-Christian deism or theism or even polytheism. Or, it could even suggest some kind of transcendent realm beyond human understanding.