When assessing claims about miracles, it is important to first consider how we judge the likelihood of any reported event. When someone tells us that something happened, we need to weigh three general possibilities against each other: that the event happened exactly as reported; that some event happened, but the report is somehow inaccurate; or that we are being lied to.
Without knowing anything about the reporter, we have to make our judgments based upon two things: the importance of the claim and the likelihood of the claim happening. When claims arent very important, our standards dont need to be as high. The same is true when the reported event is very mundane. This can be illustrated by three similar examples.
Imagine that I told you that I visited Canada last month. How likely is it that you would doubt my story? Probably not very lots of people visit Canada all the time, so its not too hard to think that I did so as well. And what if I didnt does it really matter? In such a case, my word is enough to believe.
Imagine, however, that I am a suspect in a murder investigation and I report that I couldnt have committed the crime because I was visiting Canada at the time. Once again, how likely is it that you would doubt my story? Doubts would come easier this time although it is still hardly unusual to imagine me in Canada, the consequence of error are much more serious.
Thus, youll need more than just my say-so to believe my story and will request more proof like tickets and such. The stronger the other evidence is against me as a suspect, the stronger the evidence you will demand for my alibi. In this instance, we can see how the increasing importance of an event causes our standards for believing to grow stricter.
Finally, imagine that I am once again just claiming to have visited Canada but instead of taking normal transportation, I claim that I levitated to get there. Unlike with our second example, the mere fact that I was in Canada isnt so important and it is still very believable. But while the importance of the claim being true is low, the likelihood is as well. Because of this, you are justified in demanding quite a bit more than just my word before believing me.
Of course, there is a tangential issue of importance, too. While the immediate claim might not be important itself, the implications that levitation is possible are important because it would reveal fundamental flaws in our understanding of physics. This only adds to how strict our standards for belief of this claim must be.
So we can see that we are justified in approaching different claims with differing standards of evidence. Where to miracles fall into this spectrum? According to David Hume, they fall way out at the end of the unlikely and the unbelievable.
In fact, according to Hume, reports of miracles are never believable because the possibility of a miracle actually having happened is always lower than the possibility either that the reporter is somehow mistaken or that the reporter is just lying. Because of this, we should always assume that one of the two latter options are more likely true.
Although he may be going too far is suggesting that miracle claims are never believable, he makes a good case that the likelihood of a miracle claim being true is vastly inferior to the likelihood of the other two options. In light of this, anyone claiming the truth of a miracle has a significant burden of proof to overcome.
We can thus see that the Argument from Miracles fails to offer a solid and rational basis for theism. First, the very definition of a miracle makes it almost impossible to demonstrate that a miracle claim is credible. Second, miracles are so unlikely in comparison to the alternatives that accepting the truth of a miracle would require a miraculous amount of evidence. Indeed, the truth of a miracle is so unlikely that, if one turned out to be true, that itself would be a miracle.