The philosopher David Hume was famous for saying that miracles, true or not, are not believable. True and believable are two different things.
You might say that some miracles that do not seem to want to be believable mean that we should not believe. You can use miracles as evidence that you should not believe.
Hume also claimed to show that morality is not the great believable or certain thing it is made out to be. If so, I would add that this shows miracles are lying to us when they appeal for faith in a loving God who gives moral commands, or who in some way is the same thing as moral values such as love and compassion and justice.
Even if God is not morality, the fact remains that to debunk morality is, by extension, to debunk God as well.
Or to find that morality is less clear or less useful than we are led to think is to make God not be God. If he is too unclear to guide us or be guidance, then he cannot be the being who should be at the heart of all we do. We cannot “love the Lord your God with all your heart, soul, mind, etc.” God, by definition, is that which alone ultimately matters, for all that is good comes from him.
Hume says an “is” does not imply an “ought.” A person with athletic prowess does not mean they should have it or should use it. And what about dispositions such as being unfriendly or friendly, or kind and unkind? The same applies. You cannot see how it is a rule that you must be kind just because you can be kind.
We must note that our emotions do turn an is into an ought, and feelings are a weak foundation for that, so Hume is correct. It is as if our nature has to resist logic and try to get around it. It is as if “God” made a mistake.
The fact is that people who agree with Hume are still motivating themselves by treating an is like an ought. It is human nature to do that.
Hume noticed that though you claim to take free will—as in uncaused actions or self-created actions that you bring from nothing—seriously, the reality is that you do not. You are lying to yourself. You treat you and others treat you as something predictable to a large extent.
However, the exception is how you think you have this free will and take that seriously, but do not afford the same privilege to anybody else. You like to feel you can do what you want and even turn into a serial killer, as if your goodness in the past has no influence. But that is not how you think of others.
Your devotion to the idea of free will and this form of selfishness shows that you should not be able to say, “If there is no free will, there is no morality, or morality is made less important,” with a straight face. Your version of free will is selfish, so how can it be a reliable ground of justice and love?
Hume also said that we cannot assume that every action is somehow selfish or basically self-centred. He advises us to go by “the obvious appearance of things.” That is to say, if a man lifts a bomb to save others and gets blown up, then use him as an example of selflessness and caring.
This is only a practical rule, not a moral one. He did say an ought cannot be made the same as an is, for they are two different kinds of statements. And what happens if you see the person as in denial about the destruction he is risking for himself? The appearance argument is very easily distorted and abused.
For Kant, morality is only morality when good deeds are done out of a sense of duty and obligation. Hume thinks that duty does not make an act truly good. An act, then, is good because nothing—even a sense of duty—is prompting you. It is just purely generous.
For Hume, goodness is not a duty but a habit. The good person is not one who does the duty, but one who does good without thinking, almost as a force of habit.
Religion turns into a habit, as does fervour for miracles and Masses. Yet it is about duty. None of this makes sense. Religion and the things related to it, such as prayer and miracles, are incoherent.
We conclude, then, that Hume, if he had teased out the implications of some things he wrote, could have come up with more refutations of the credibility of miracles and God.