prior probability

We’ve been meaning to write up a scholarly critique of Richard Delgado’s law review article titled “A plea for narrative,” which was published in the pages of the Michigan Law Review, vol. 87 (1989), pp. 2411-2441. (Professor Delgado’s classic paper has been cited over 2600 times according to Google Scholar, and it was assigned reading for the first annual Margaret Montoya Legal Writing Retreat that we attended last month.) So, without further ado, here it goes: while we generally that lawyers are essentially storytellers and that stories are a forceful means of communicating ideas, there are three potential problem with storytelling. Professor Delgado identifies two of these perennial problems in footnote 87 of his paper (internal citations omitted):

There are dangers in storytelling …. The hearer of an unfamiliar [story] may reject it, precisely because the story unmasks hypocrisy and increases discomfort. *** Or, the hearer may consciously or unconsciously reinterpret the story, in light of the hearer’s own belief system and inventory of stock stories, so as to blunt, or even reverse [!], its meaning.

In other words, stories can actually strengthen the audience’s preexisting biases (the problem of confirmation bias) or produce an unintended polarizing effect (the problem of polarization). But these problems, in turn, are symptoms of a much deeper storytelling dilemma, one that Delgado does not address in his essay. I will dub this dilemma the “truth-value problem.” (This quandary is also referred to pejoratively as “just-so stories” in the philosophy of science literature. According to Wikipedia, a just-so story is “an unverifiable narrative explanation for a cultural practice, a biological trait, or behavior of humans or other animals.” As a further aside, Professor John Alcock writes in his 2003 book The Triumph of Sociobiology that the term just-so story is “one of the most successful derogatory labels ever invented.”) But as Professor Delgado correctly notes in his 1989 paper, storytelling is not just an indispensable feature of law practice; it is also a crucial part of human culture. So, how are we to respond to the “just-so story” label?

One response is to openly acknowledge the truth-value problem. Another response–one consistent with Professor Delgado’s scholarly project–is to tell better stories. (Exhibit A: Harper Lee’s “To Kill a Mockingbird.”) Yet another response is to change the incentive structure of scholarly work by rewarding “academic storytelling.” Most legal scholarship is either descriptive (telling us how what the law is; i.e. how the law plays out in the real world) or normative (telling us what the law ought to be; how the law should play out in an ideal world). There is no reason in principle why we can’t have a third category of “scholarly storytelling.” Even if most such stories in this third canon are unable to counteract or negate the polarization, confirmation bias, and truth-value problems we have identified in this post, all it takes is a few good stories to enrich our understanding of the world …

In case you’ve ever wondered what would happen if artificial intelligence were trained to perform image captions of Rorschach inkblots, this crazy website created by researchers at the MIT Media Lab is for you. Here are some sample Rorschach inkblots with AI generated captions:

Hat tip: kottke.

SCOTUS announced its decision in the Colorado gay wedding cake case yesterday (4 June). In brief, the Court side-stepped the main substantive issue (is baking a wedding cake a form of expression under the First Amendment?) and decided the case on procedural grounds instead: litigants are entitled to a neutral decision maker, even in administrative law cases! (See, in particular, Part III of the Court’s majority opinion, pictured below.) In other words, this is more of a Fourteenth Amendment case (procedural due process) and less of a First Amendment case (free exercise of religion).

#PassiveVirtues #AlexanderBickel

As we mentioned in a previous post (part 4 of our review of Allen and Pardo’s relative plausibility paper), “plausibility”, however defined, is just another word for “probability.” Yet, this notion of plausibility, though simple and intuitive, is a crude concept at best–not because it eschews the use of numerical values; but rather because it expresses only one shade of the probability continuum. It turns out there are many different words and phrases to describe many different levels of probability. [See chart below. More details are available here (via Wikipedia) and here too (via the CIA Library).] The main point (the one most relevant to the legal proof literature) is that we don’t always need to express our probabilities (or subjective degrees of belief) using numerical values. Words can work just fine, but we will need more than one word.

We have been reviewing Ron Allen and Mike Pardo’s excellent paper on “relative plausibility,” and as we mentioned in our previous post, we commend their relative plausibility theory of juridical proof for its simplicity. In brief, their theory is that jurors in civil and criminal cases compare and evaluate competing explanations of the evidence presented at trial. In civil cases, where the standard of proof is the preponderance of the evidence, the side with the most plausible explanation of the evidence, i.e. the side who offers the best explanation of the evidence, wins. In criminal cases, where the standard of proof is beyond a reasonable doubt, the defense wins if it offers any plausible explanation of the evidence consistent with the accused’s innocence. Continue reading →

In our previous post, we restated Ron Allen and Mike Pardo’s “relative plausibility” theory of legal proof (or what Allen and Pardo also call the “explanatory account” of evidence), an approach meant to displace probabilistic or mathematical theories of legal evidence. Briefly, according to Allen and Pardo, jurors don’t engage in highfalutin probabilistic reasoning when they decide civil or criminal cases. Instead, they simply compare and contrast the stories of the plaintiff and the defendant, and the party who offers the best explanation of the evidence—i.e. the party with the best* story—wins. (*Of course, the meaning of “best” in any given case will depend on the burden of proof used to decide the case, such the preponderance standard in civil trials or the reasonable doubt standard in criminal ones.) Continue reading →

As we mentioned in a previous post, law professors Ron Allen and Mike Pardo summarize and critique probabilistic theories of evidence on pp. 7-12 of their most recent paper “Relative plausibility and its critics.” (Hold on: “critique” is too polite. They launched a blistering attack!) In addition, they also present an attractive and intuitive alternative theory of legal trials in their paper. Without further ado, here is how they describe their theory of  “relative plausibility” in their own words (pp. 13-14, footnotes omitted):

“Rather than characterizing proof standards as probabilistic thresholds (such as 0.5), [our theory of] relative plausibility accounts for the standards in terms of explanatory thresholds. 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. *** The explanatory thresholds vary depending on the standard—with higher standards requiring a higher threshold. Under the ‘preponderance of the evidence’ standard, fact-finders determine whether the best of the available explanations favors the plaintiff or the defendant. The best available explanation will favor the plaintiff if it includes all of the legal elements of plaintiff’s claim; it will favor the defendant when it fails to include one of more elements. A number of general criteria affect the strength or quality of an explanation. These criteria include considerations such as consistency, coherence, fit with background knowledge, simplicity, absence of gaps, and the number of unlikely assumptions that need to be made.”

This relative plausibility theory of legal proof is itself very plausible and intuitive. Alas, this theory does not banish the specter of probability from the trial process, for the word “best” is just code for “more probable”, whether we assign a numerical value or not to describe the level of a story’s plausibility! (See image below, by way of example.) Stay tuned, we will weigh the pros and cons of Allen and Pardo’s relative plausibility theory in our next two blog posts …

CNN, the first television channel to provide 24-hour news coverage, went on the air on this day in 1980. At the time, CNN’s format was a radical innovation. Today, with the rise of the Internet, CNN–and cable TV generally–seem so antiquated …