Carl Sagan helped popularize the phrase “extraordinary claims require extraordinary evidence”. You often hear this phrase chanted like a mantra when talking to skeptics. This maxim is derived from the famous Scottish philosopher David Hume, who argued that miracle claims can never rationally be believed. Says Hume,
It is experience only, which gives authority to human testimony; and it is the same experience, which assures us of the laws of nature. When, therefore, these two kinds of experience are contrary, we have nothing to do but subtract the one from the other, and embrace an opinion, either on one side or the other, with that assurance which arises from the remainder. But according to the principle here explained, this subtraction, with regard to all popular religions, amounts to an entire annihilation; and therefore we may establish it as a maxim, that no human testimony can have such force as to prove a miracle, and make it a just foundation for any such religion.
In other words, Hume is saying that mankind’s experience of the world has well-established that the laws of nature are essentially ironclad. In order to believe the testimony of a miracle, one would need more evidence than all of humankind’s experience of the laws of nature, which of course is impossible. On the other hand, we often experience that people at times lie about what they’ve seen or are simply mistaken. The probability against a miracle is extremely high.
There are a lot of problems with Hume’s argument, but I want to focus on his use of probability. Hume only considers one part of the equation. Hume says that since miracles are by definition improbable events, we are irrational to accept that a miracle ever occurred. Given our knowledge of the world, this overwhelms any evidence that can be offered. Rather than asking ourselves of how improbable that a miracle did occur, what we need to be asking ourselves is “what are the chances that a miracle did not occur given the specific evidence that we have? ” We can’t just write off miracle claims with the wave of a hand as Hume and his skeptic followers would like us to.
Unless we’re just prejudiced naturalists, we need to also consider what is the probability of other hypotheses that can be offered. For instance one might look at the evidences for the resurrection of Jesus. The probabilities of the naturalistic hypotheses (as I’ve briefly discussed here, and you can also read here and here for more detail) are really low. One cannot just look at the resurrection with just our basic knowledge of the world and say it never happened. With some help from Bayes Theorem, the probability of the resurrection might actually come out to be quite high when the alternative explanations are factored in. Going all nerd here, such an equation would look like this:
Pr (M/K&E)= Pr (M/K) × Pr (E/K&M)/Pr (M/K) × Pr (E/K&M) + Pr (not-M/K) × Pr (E/K& not-M)
- Pr= probability
- M= miracle
- K = general knowledge of the world
- E= evidence
The miracle hypothesis would gains probability as the alternative explanations are demonstrated to be improbable. So when we look at the full scope of the evidence and see that the hallucination theory, wrong tomb theory, or the conspiracy theory are shown to fail in explaining the full scope of the data, the miracle hypothesis – which does cover the full scope of the data quite well – becomes more and more probable in comparison.
Moreover, who is to say that natural law is uniform? Only if we presuppose that naturalism is true would we conclude that nature is as uniform as Hume would lead us to believe. If we assume that God does not exist or He does not act in the world from the start, then of course miracles are extremely improbable. But if God exists and He is a free agent, He can put his stamp of approval on whatever pleases Him. He might want to heal a cancerous person because He sees their faith, or in the case with Jesus of Nazareth, God may decide to resurrect him as an endorsement of his claim to be the Son of God.
In his classic work A View of the Evidences for Christianity, William Paley asks rhetorically “In what way can a revelation be made but by miracles?” Paley’s answer is tersely straightforward: “In none which we are able to conceive.” In other words, if there is a God who wishes to unmistakably show Himself to us, miracles are not improbable, they are unavoidable.