As I mentioned in my previous post, this week I will offer my own lawyerly take on David Hume’s influential argument against the possibility of miracles: the good, the bad, and the ugly. Let’s start out on a positive note, shall we, with “the good”? (Rest assured, I will consider “the bad” and “the ugly” sides of Hume’s anti-miracle essay in subsequent posts.)

Simply put, what I like the most about Hume’s argument is his lawyerlike and probabilistic approach to the problem of miracles. For Hume, whenever you read or hear a report of a miracle or some other remarkable event — whether it be a UFO sighting, a levitating saint, or Lazarus’ resurrection from the dead — you should weigh the evidence based on your own experience and common sense. Specifically, Hume proposes a two-part probabilistic test for weighing the evidence.

In summary, the first part of Hume’s probabilistic test requires us to assign two separate probability values to the evidence as follows: the probability p₁ that the miracle really happened and the probability p₂ that the evidence is either mistaken or fraudulent or otherwise defective. The second part of Hume’s test is to compare p₁ and p₂. To the point, you should believe in the miracle only if p₁ > p₂.

Moreover, Hume’s exhortation to weigh the evidence is exactly what juries do when deciding law cases. In fact, Hume’s simple probabilistic test reminds me a lot of my colleagues Ron Allen and Mike Pardo’s “storytelling” account of legal proof. (See Ronald J. Allen and Michael S. Pardo (2008), Juridical proof and the best explanation, Law and Philosophy, Vol. 27, pp. 223–268, which is available here. See also Allen & Pardo (2019), Relative plausibility and its critics, International Journal of Evidence & Proof, Vol. 23, pp. 5–59, available here.)

Among other things, Allen and Pardo’s account of legal proof not only makes intuitive sense; their storytelling approach also parallels Hume’s probabilistic two-part test for miracles:

“The proof process involves two stages: (1) the generation of potential explanations of the evidence and events, and (2) a comparisons of the [plaintiff’s and defendant’s competing] explanations in light of the applicable standard of proof. In general, the process depends on the parties to obtain evidence and to offer what they consider to be the best explanation (or explanations) that support their respective cases.” (Allen & Pardo 2019)

In other words, when jurors are deciding cases, what they are really doing is comparing the competing stories of the plaintiff and the defendant, and it is the party who offers the best explanation of the evidence — i.e. the party who tells the best story — who wins. Sound familiar?

This storytelling account of legal proof — like Hume’s probabilistic test for miracles — also has two major virtues. One is that it makes the most intuitive and descriptive sense: jurors do tend to weigh the evidence presented at a trial holistically, and they tend to favor the side whose story is more persuasive, or to borrow Allen and Pardo’s terminology, juries usually prefer the side whose story offers the best explanation of the evidence. The other virtue of the storytelling approach is an aesthetic one: its elegant simplicity. Why is simplicity a virtue? Because more simple or parsimonious explanations are almost always better than complex or convoluted ones, a fundamental principle called “Occam’s Razor”.

Nevertheless, Hume’s probabilistic test, along with Allen and Pardo’s storytelling approach to legal proof, has two big blind spots: (1) the reference class problem, and (2) the unknown probability problem. Stay tuned: I will explain both of these fatal flaws and present an alternative approach to the problem of miracles in my next few posts.