Hume said a miracle is a violation of what we know about nature, so if somebody says they see one, we have to assume this is too unlikely, so it is more likely they are mistaken or lying. It is not true that he said a violation of nature is impossible, so a miracle claim is necessarily false. His work on cause and effect shows that he did not regard nature as that ironclad in its working. The idea that Hume thought the universe was a system necessarily closed to God's, or supernatural, intervention is an exaggeration.
He did say that you need a virtually miraculous case for saying a miracle is real, given that human nature is so prone to lying and making mistakes. A good way to word this is if you say when your house was burgled by humans, you don't need the same evidence as you do to say chimps did it. And imagine the evidence you would need for something so unbelievable, albeit conceivable. Imagine what you need if you say Jesus Christ appeared and did it. That is out of the natural altogether.
Hume – like everybody else – noticed that even without a demand for miraculous evidence, what is offered up to now falls short. There is no hard evidence, for example. Any report verifying a miracle can be countered with one saying otherwise. There is always a window for error or lies.
Christians say, "A miracle occurs when the world is not left to itself, when something distinct from the natural order as a whole intrudes into it." It has been noticed that very few Bible miracles are nature behaving in a new and unknown way. Most Bible miracles are done through agents. They don't try to act as if nature is being violated. What happens is some person is chosen by God for God to act through. God, instead of helping people directly, gets people like Elisha and Jesus to do it for him.
So they hesitate about a God being the agent. They say it's wiser if only human agents act for God and with his authority. This is probably because they see a miracle not as an attempt to fix something that has gone wrong, but as a sign that God recognises the teaching of the agent. The agent is effectively a messenger.
Their argument shows some embarrassment about, say, thousands needing food and food just appearing. They like the notion that Jesus had to be involved to multiply the food. But if some power multiplies the food, the point is that a power is doing it. It would not matter if there were an agent or not. The Christians are using the agent thing to distract from the absurdity. The agent only tries to help and never says why the miracle happened or what message it is giving. The religious say miracles are signs, but if there is no message, then it does not matter if a blind man gets a cure without an agent or with one. And just because the agent is there, it does not mean that the agent is really an agent. A witch can turn you into a toad with a spell, or she can cast a spell and, coincidentally, magic turns you into a toad and her spell had nothing to do with it. Two things happening together is as likely to make them connected as it is unconnected.
No agent was there when Jesus supposedly rose. No human agent asked Jesus to appear after his death. No agent was there when the pagan girl recovered from demonic possession. No agent was there when soil turned into a man, Adam. No agent took his rib out to make Eve. No human agent asks for Mary to appear at Lourdes, etc. Yet you have the visions to Bernadette in 1858.
Surely they don't mean that Hume is right but only when a miracle has no agent? Do they think that a house building itself is out? This is arbitrary, for if Jesus tells it to build itself and it does, it might have an agent but there is no relevant difference. What if nobody knows Jesus told it to? That does not make him any less of an agent.
The problems with miracle belief show that believers, in fact, may be in denial that they agree with him or largely agree with him. They surely admit that there could be a miracle they don't know of that could displace the credibility of Jesus' resurrection. For example, twelve reliable people who we know see a statue of Zeus coming to life for a day. It gives a message and perhaps says nobody rises from the dead. That overrides twelve people who never wrote their experience down as it happened, and who we don't know, and who say Jesus appeared to them risen.
Hume did agree with belief in a miracle if the case was good enough, but the standard was admittedly high but not insurmountable. Even if we could not get to actual firm belief in any particular claimed miracle, we should have enough to justify considering it seriously. And we do not.
It does not matter if the investigative standard is low or high. A miracle's alleged value and message is cancelled out by another one that contradicts it.
You hear, “It was philosophers such as Hume who said that about belief in miracles, not scientists.” Actually, Hume only did the wording. Scientists would not have been so dedicated to experimentation if they believed that some force could make an apple tree grow bananas. Or if some force could make them miraculously make the mistake that this happened. They tested and re-tested assuming that anything odd would be a sign that a mistake or lie had occurred. This is about stopping people from saying that the impossible happened, for that is an absurdity and threatens all logic and truth.
It is about stopping people from mistrusting the findings of science on the basis that something might have tampered. A supernatural being can use nature or even the supernatural so that you cannot detect that any interference occurred. The rose flowering seems natural and might not be. A magician uses nature to deceive, so a supernatural being can do that too.
Hume is accused of denying that an “intrinsically improbable event is the most probable event given the evidence.” He certainly knew that a person can break a record. But a miracle is not the same kind of claim. It is outside the way nature works. Hume says that a miracle violates what our experience confirms as something that does not happen. He is said to call testimony to a miracle unreliable. But what if he means not that it is unreliable, but that it is shouted over by a stronger voice? Miracle believers have to admit that there could be a shouting over that they don't know of yet. They want you to say that the supernatural doing things in this world is not contradicting natural law, for the natural has its system and the supernatural has one of its own. But that does not guarantee that their pet miracles will be shown to be the best examples or even plausible.
Finally, like the rest of us, scientists do think like Hume. Believers do as well, but then they cherry-pick miracles so that is not as plain as it might be. Religion is not really as respectful of miracle and believers in miracles as it pretends.
Suppose I agree with Hume. Suppose then I hold that the miracle I consider valid on his criteria is, say, Leonora Piper's mediumship. Or a sign that told me Jesus rose, yes, but miraculously died again. Believers will not respect my view. They will ignore it. Attacks on Hume are too much about protecting not rational religion but protecting superstitious notions.