John Loftis, at his blog Debunking Christianity, lists ten objections, concepts, or topics that seem to be raised most often by atheists in debates with theists. Over the course of the next week or so, I'd like to comment on each of them. Here's the first:
1. Extraordinary claims require extraordinary evidence. Consequently, the burden of proof is on the theist rather than the atheist.
This notion (let's call it ECEE for short) is the legacy of skeptic David Hume and 19th century evidentialist William Clifford and popularized in recent times by Christopher Hitchens. It's often used as a way to minimize or disregard testimony of the occurrence of a miracle. A miracle is such an extraordinary event that it should take extraordinary evidence to persuade someone that the event really is veridical.
There are at least three problems with ECEE, however. One is that it's self-refuting. It's a claim, extraordinary or not, for which there's no evidence so why accept it? Another is that the word "extraordinary" can be a little fuzzy. For example, the claim by a friend that he won the lottery is certainly extraordinary but the evidence he adduces in support of the claim, a lottery ticket with the winning number on it, is not extraordinary, at least not in the same sense.
A third problem is that it's not at all clear what counts as extraordinary evidence. Consider reports of a miracle such as the Resurrection of Jesus. It's a very extraordinary claim, to be sure, but how much evidence would it take to satisfy the demands of the ECEE? Both Hume and Clifford make it clear that no amount of evidence would be enough, and if that's the case the ECEE is really just intellectual camouflage for the person who simply doesn't want to believe it.
Another difficulty is that skeptics are very selective in their application of ECEE. For example, they often will accept the claim that there are an infinity of other universes in a multiverse, that the world just popped into being out of nothing or, alternatively, that it's infinitely old, that life arose mechanistically from non-life, that all forms of life are the product of blind, impersonal forces, that consciousness can be explained purely in terms of material structures, that there is no immaterial substance, etc. all of which are extraordinary claims for which there's either no evidence at all or scant unambiguous evidence.
Finally, what's important about evidence is the difference between the probability that an event occurred given our background knowledge of such events and the probability that the evidence we find would exist if the event hadn't occurred. In other words, the probability that a man might rise from the dead is certainly very low given our experience in the world, but the probability that the tomb would be empty, the disciples not arrested for stealing the body, the body not being produced by the authorities, the reports by hundreds of people of having seen the risen Christ, the willingness of the disciples to die for their belief that they had personally seen him, and so on, had Jesus not risen from the dead, is also very low.
So, given that both probabilities are low and in fact are inscrutable, it's hard to see how the ECEE really bears on at least this one crucial miracle.
Finally, a closing thought about the second sentence in #1, above: The burden of proof is always on the person who makes an affirmation. If the theist claims that God exists then he has an obligation to give sound reasons for accepting his claim. If the atheist denies that God exists then he has an obligation to give sound reasons for accepting his claim. Only the agnostic is absolved of the responsibility for giving reasons.