As amusing as I found this xkcd cartoon, it illustrates a couple of common logical fallacies. The first is the faulty analogy, the second is shifting the burden of proof.
The faulty analogy in the above cartoon comes from the fact that ones belief in God, especially a three O God, is not comparable to belief in an alien twin. This twin would be much like you, and so wouldn’t have any more influence on your life than you have influence on life on another planet, should there be any. This entity is unlikely to offer you any afterlife, let alone one that would provide the comfort that religion tends to offer. Conversely, deities are assumed, by believers to influence peoples lives, and offer a comforting, or not so comforting afterlife. An analogy needs to share enough characteristics, that all arguments for the issue in question can be transposed to the analogy.
Shifting the burden of proof is a common hiding place when ones beliefs are challenged and no solid proof exists for that belief. Some beliefs are based on a burden of proof in the form of evidence that, interpreted in a particular way, stacks up to form reasonable evidence to assume proof. In these cases, critics will try to erode the evidence by reinterpreting it to suit their point of view, or by proving the evidence wrong. What sometimes happens is the protagonist of a particular viewpoint then says, “well, you can’t prove it isn’t the case,” as in the cartoon above. This is a poor argument, and is most commonly used by religious groups, but I have heard Big Bang supporters using it too.
Consider the following scenario, which appears in various forms:
I have an apple, which is red inside and out, but if you damage it in any way, the inside of the apple becomes white. Prove me wrong.
As the proposer of the red inside apple, the burden of proof lies with me, particularly since proving it wrong would be highly problematic. It’s unlikely that I would be able to prove it through testing, so I’d have to argue for it being a rational idea, then support it with certain empirical facts which I could argue support such a hypothesis, it would also help to argue that the arguments against my idea are invalid.
That concludes this weeks fallacy, you get two, and a cartoon to boot.