If I engage a believer in a conversation about faith, I will most likely get a story about miracles. Belief in miracles is the cornerstone of faith for most people, and this has always struck me as somewhat peculiar. If we take faith, by definition, to be belief that extends beyond the scope of justification, it is odd that virtually every person of faith holds miracles up to be a good reason, i.e., justification, for believing in God. It is especially odd in light of the fact that belief in miracles would only count as good evidence for belief in God if that belief is itself justified by evidence. In other words, the occurrence of miracles only counts as good evidence of the existence of God if there is good evidence that miracles have occurred. I don’t think that there is any good evidence for the occurrence of miracles, but I don’t see the point in showing the error of specific claims of miracles with a magnifying glass and a flashlight. Belief in miracles is never justified because of what a miracle is. The following is a brief explanation of this problem.
Sometimes the word "miracle" is used loosely, e.g. "Every baby is a miracle," or "Getting an ‘A’ on my test was a miracle." But when people appeal to miracles in a theological debate, they mean breaks in the laws of nature. If science can predict and/or explain an event, we don’t take it to be miraculous. Instead, believers hold up events that appear to be scientifically inexplicable as evidence for Divine (supernatural) intervention. The reasoning goes like this: This event can’t be explained by appeal to a natural cause, so, the better explanation is that it must have been caused by something supernatural (God). In order for this argument to be sound, the believer must demonstrate that the following presumptions are justified:
A) Every natural (physical world) event must be caused by some previous event.
B) Super-natural (non-physical) entities can cause physical events.
C) The best explanation for mysterious events (ones without an obvious natural cause) is that they have a supernatural cause.
If any of these assumptions fails, then the conclusion that a miracle is the best explanation for a mysterious event is not justified. And, if belief in miracles is unjustified, then belief in God based upon the "evidence" of a miracle is also unjustified. So, let’s look at at whether these assumptions can be defended.
Assumption A is close to being an axiom of science. Though most scientists would agree that some quantum events don’t appear to be caused by anything, the assumption that physical events are caused by prior physical events is fairly uncontroversial on the level of everyday observable phenomenon. If your car starts making a thumping noise and the mechanic says there is no cause, you find another mechanic, you don’t question causal necessity. So, for the time being, let’s bracket Assumption A and take it for granted.
Assumption B sounds reasonable if you’ve never considered the meaning of the word "cause," but it falls apart under conceptual scrutiny. The concept of a non-physical cause is problematic because our normal use of the term pertains exclusively to events in the physical world. For example, the heat of the liquid caused the cold glass to shatter, or the finger on the trigger, caused the gun to fire. These are physical causes. It is difficult to imagine what a non-physical cause for a physical event could be. Some might argue that beliefs are the non-physical cause of actions, but if beliefs were non-physical causes, then manipulation of the brain wouldn’t necessarily affect either beliefs or actions, as we know it does. The fact that brain states, not the stated beliefs of the agent, are the best predictor of action demonstrates that there is a physical cause underlying the phenomena. It also illuminates another problem with appealing to non-physical "causes," namely that they are explanatorily useless.
This brings us to Assumption C, which is really the foundation of the miracles argument. People believe in miracles when they conclude that an act of God/magic is the best explanation for a mysterious event. This begs the question, "How does positing the existence of supernatural causes explain anything?" When we assume that physical events are caused by previous physical events that follow patterns of law-like regularity we are able to make lots of predictions that enable us to navigate the world. So, Assumption A is practically useful. The truth (or approximate truth) of A is also the best explanation for why we are able to make consistently successful predictions when we assume it. In contrast, Assumption C is neither practically useful nor likely to be true. We can’t predict anything new by positing that there are supernatural interventions into nature, and the best explanation for why supernatural explanations are consistently replaced by natural explanations (e.g., hearing voices is schizophrenia, not demonic possession) is that supernatural causes aren’t real.
We don’t have a good reason to believe in miracles because we don’t have a good reason to believe in supernatural causes. In fact, the whole notion of a non-physical cause is conceptually confused. Saying ‘God caused the event’ is just as explanatorily informative as saying ‘nothing caused the event’, and we have no more reason to believe in the former than in the latter. It is, of course, possible that there are are supernatural interventions into nature, just as it is possible that some events are entirely uncaused by anything, but neither of these assumptions jibes with the majority of our experiences, and neither of these assumptions tells us anything useful about the world.
Positing the occurrence of miracles is never the best explanation for mysterious events. We have lots of reason to believe that strange events can and will be be explained by natural science because so many previously mysterious events have been explained by science. But even if we can’t explain the physical (natural) cause of an event, we have no good reason to believe it was supernaturally caused. The possibility of a miracle doesn’t answer any questions, it just begs them.