Hume on Miracles: What Does it Mean That “Extraordinary Claims Require Extraordinary Evidence”?

Part I of a series on the resurrection

Statue of David Hume. Photo by K. Mitch Hodge on Unsplash (quote from Hume added by the article author)

Carl Sagan’s “extraordinary claims require extraordinary evidence” is a witty summary of Hume’s argument against miracles.

But can we be more specific? Are miracles impossible? Unjustifiable? Or something else? Leading modern philosophers (like JH Sobel) have refined Hume’s arguments. This article builds on their work to set out clear criteria for evaluating the resurrection.

Are miracles impossible?

Some use Hume’s arguments to justify their belief that miracles are impossible. However, Hume rejected this view:

there may possibly be miracles, or violations of the usual course of nature, of such a kind as to admit of proof from human testimony

(quoted in Sobel, JH. Hume’s Theorem on Testimony Sufficient to Establish a Miracle. Philosophical Quarterly 1991; 41:229–237)

Criteria for a justified miracle claim

Hume stated his criteria with familiar panache:

That no testimony is sufficient to establish a miracle, unless the testimony be of such a kind that its falsehood would be more miraculous, than the fact which it endeavours to establish.

Yet, there is ambiguity in how we should apply these criteria. Sobel, a leading atheist philosopher, proposed the following interpretation.

(where A=a miraculous event, α=testimony for A, ~A=miraculous event did not happen)

1. P(α) > 0 & P(A| α) > 1/2

• probability greater than zero for testimony about the miracle
• probability of a miracle happening (given testimony about the miracle) is more likely than not

2. It follows from 1. that P(A & α) > P(α & ~ A)

• the probability of a miracle and testimony about the miracle P(A&α) is greater than the probability of that testimony when the event didn’t happen P(α & ~ A)

Others, such as John Earman, propose similar definitions such as:

P(A|α) > P(α|~ A)

• the probability there was a miracle given the testimony of a miracle P(A|α) is greater than the probability of the same testimony but no miracle P(α|~ A)

Defining laws of nature and miracles

How we define laws of nature depends on whether we see these laws as complementary, or in conflict, with God’s intervention in the universe.

For atheist philosophers, like David Hume or Paul Draper, miracles are a supernatural intrusion on the natural world:

Thus, it is this sort of direct divine activity that involves the violation of laws of nature and so brings theistic religions into conflict with a scientific understanding of the world. (Draper, God, Naturalism and Science)

However, Peter Harrison (a historian of science) has argued this definition:

implies that an unproblematic distinction can be drawn between ‘natural’ and ‘supernatural’, and that this distinction was routinely operative in the history of science. This turns out to be mistaken. (Harrison, Naturalism and the success of science. Religious Studies 2020; 56: 274–291, p275)

In contrast, theists like John Polkinghorne, formerly professor of mathematical physics at Cambridge University, consider the laws of nature reflect God’s constant activity in the world. Therefore, these laws:

…are not the grain against which a wonder-working deity occasionally acts, but their regularities are the pale reflection of the faithfulness of the Creator. (The Faith of a Physicist: Reflections of a Bottom-up Thinker, p79)

On this definition, the laws of nature reflect God’s regular activity upholding the universe. Since these laws depend on God, he is free to change how these work on isolated occasions.

Background knowledge

For those who consider the laws of nature and miracles as competing explanations — the prior probability of a miracle is how often we experience the laws of nature to be fixed.

For example, the laws of nature in our universe determine that when we die our bodies decay. There are no known ‘natural’ exceptions to this law.

Therefore, for Hume, when someone testifies about a miraculous event it is always more likely the event never happened (P(α & ~A)) than if it did (P(A&α)).

As seen above, this assumes the laws of nature and God’s intervention are mutually exclusive. But if there is a God, it is at least possible, he could choose to depart from his usual operation of the regularities of the universe:

But any theory showing whether laws of nature are ultimate or whether they depend on something higher for their operation is crucially relevant. If there is no God, then the laws of nature are the ultimate determinants of what happens. But if there is a God, then whether and for how long and under what circumstances laws of nature operate depends on God. (Richard Swinburne, Resurrection of God Incarnate)

Sketching out what evidence is required

Bayesian network of key factors to consider when evaluating evidence for Jesus’ resurrection

So background knowledge will depend on the following:

• the likelihood of existence or non-existence of a God capable of departing from the laws of nature
• the likelihood of resurrection if God doesn’t exist
• the likelihood of resurrection if God exists
• how likely that God is to intervene- in the case of Jesus how likely God is to send a Messiah
• the historical evidence on how likely Jesus was the Messiah

The historical evidence will depend on the following:

• the likelihood of evidence for resurrection if God exists and Jesus was resurrected p(α|A&T)
• the likelihood of evidence for resurrection if God exists and Jesus was not resurrected p(α|~A&T)
• the likelihood of evidence for resurrection if God does not exist and Jesus has not been resurrected p(α|~A&~T)