Often Theists and Atheists who engage in debate find themselves wondering just how much evidence or reason they each have the responsibility to offer the other. A Theist who takes belief in God to be properly basic may be waiting for some defeater, whereas the Atheist might think, since they have no responsibility to prove a negative, they don’t have to offer any arguments either. I think the epistemology of the theist is broad foundationalism and reliabilism. The epistemology of the atheist is… probably the same. Usually, in a debate, the Theist knows better than to say something like “well, it’s obvious, isn’t it?” Instead they will offer arguments. Atheists, often unsophisticated atheists, will, however, say that it is not their place to offer such arguments, since their position is simpler. They have the advantage of being able to criticize theistic arguments without the disadvantage of having to submit any of their arguments to criticism. This, they figure, is legitimate because they aren’t trying to prove anything, but only trying to demonstrate that Theism cannot be proven. Many of them explicitly say that one cannot prove a negative, and say that nobody thinks they have to prove that fairies don’t exist when they fail to believe in them – why should monotheism be any different. Of course, to the Theist this sounds rather like saying “nobody has to prove fairies don’t exist to be justified in not believing in them, so why not anything else, like the existence of other minds, or the external world, or free will?” The atheist may respond that people who failed to believe in those things would have a responsibility to explain why, but somehow the case of Theism is different – it isn’t properly basic.
Two things need to be responded to this kind of atheist. First, in the context of a debate one is expected to present arguments for or against the proposition in dispute, and if the atheist really wanted only to debate whether or not the existence of God can be proven, then she should have entered a debate with the title “can the existence of God be proven?” instead of “does God exist” or something to that effect. However, even in casual conversation atheists will often not give any arguments for their atheism, and appeal to the response mentioned above, that there are no ways to prove a negative. So, one needs simply respond that this just isn’t true. One can prove a negative, and in a number of ways.
There are two ways to deductively prove the non-existence of God. First, by attempting to show that it is self-referentially incoherent in the same way that the concept of a married bachelor is, and second by showing that it is self evidently false by reason of a necessary deduction from facts which are themselves self-evident. If the concept of God necessarily involves a logical contradiction then it ceases to be cognitively meaningful, and therefore there is no logically possible world in which “God exists” can be interpreted to be true, just as there is no logically possible world in which a square-circle can instantiate. Second, one could try to prove from facts which are themselves self-evident, such as that an external world exists, or more probably that such a world involves instances of evil, that the proposition “God does not exist” is logically entailed by these.
Apart from this, one could construct a probabilistic argument against God. For instance, although it is, in the simplest sense, axiomatic that absence of evidence is not evidence of absence, absence of evidence CAN act as evidence of absence when and where the absence of evidence runs contrary to the predictions of the theory or postulate. For instance, as William Lane Craig has said before, consider the postulate that fairies exist: we might have expected to have run into them, or else encountered their corpses, homes, clothing, or what have you. Therefore, under certain conditions absence of evidence can be properly taken to be evidence of absence. This is the logic behind Victor Stenger’s argument from the absence of prayer’s observable efficacy. Of course “empirical proof” is technically an oxymoron, but one might still do well to consider the weight of empirical evidence for or against a proposition.
That provides a number of ways for the Atheist to go about proving or demonstrating that there is no God. Furthermore, (and this is more important) one should not be shy about pressing the atheist to define what kind of atheist she is. There are only three different kinds of atheism. Agnosticism is technically Atheism insofar as an Agnostic lacks any positive belief that there is a God. Thus, in this sense, everything from a philosophical agnostic to a new born babe, and to a fly on the wall, qualifies as an ‘Atheist’. On the other hand, Strong or Positive Atheism is the positive belief that there is no God and nothing like God. Douglas Adams has a quote I can’t help but use here, where he describes himself as a ‘radical’ atheist:
Yes, I think I use the term “radical” rather loosely, just for emphasis. If you describe yourself as “atheist,” some people will say, “Don’t you mean ‘agnostic’?” I have to reply that I really do mean atheist, I really do not believe that there is a god; in fact, I am convinced that there is not a god (a subtle difference). I see not a shred of evidence to suggest that there is one … etc., etc. It’s easier to say that I am a radical atheist, just to signal that I really mean it, have thought about it a great deal, and that it’s an opinion I hold seriously.
— Douglas Adams, from an interview with American Atheists; quoted from Warren Allen Smith, editor, Celebrities in Hell (2002); excerpted by Positive Atheism (2007)
A Strong, or Positive, or ‘radical’ atheist, then, is somebody who has seriously considered the question and has come to the conviction that there simply is no such being as God. This is probably the most common kind of atheist, and these should not be allowed to hide behind Agnosticism. Since they have the positive conviction that God does not exist the theist has every right to demand of them some reasonable account for their positive belief that God does not exist.
Finally there are verificationists or ‘non-cognitivists’ who argue that the proposition “God exists” is simply cognitively meaningless. These are usually the most philosophically sophisticated of the three and they cannot give any reasons why they think God does not exist precisely because they don’t have any idea whatever what the proposition “God does not exist” means.
It is legitimate to ask the atheist who has chosen to dialogue on the issue which camp they fall into, and to treat them accordingly. In the first camp, the theist simply must try to offer some persuasive and compelling reasons for God’s existence. In the second camp, the theist should offer arguments along with trying to dissolve those problems which have led the atheist to the conviction that God does not exist. Finally, in the third, the Theist must simply try to begin by defining God in ways that make it possible for the non-cognitivist to really understand the proposition.
One must decide which of the three they identify with, and if the second then they have as much burden to present the reasons for their rejection of the proposition as a theist has for offering reasons why they think the proposition is true. The burden of proof is not completely on the Theist if the topic is “does God exist” and the Atheist represents the negative response.
Two things which must be kept in mind by theists when encountering atheists like this: the belief in God may still be properly basic for the theist, and thus the theist need not necessarily feel obliged to gather arguments for theism to feel justified in their theism, even while gathering arguments for the sake of apologetic demonstration to the atheist. Second, the Theist should take inventory of just how many good arguments for the existence of God exist, and when an atheist inquires, searching for some reason the theist might have for believing God exists, the theist has an opportunity to share and discuss many of these arguments. One should not feel shy about forcing the atheist to reveal what kind of atheist they are, and then continue the conversation with that in mind, comporting oneself with respect and understanding for where that particular atheist is coming from.