February 16, 2008


The first chapter in Tobias Jones' The Dark Heart of Italy is "Parole, Parole, Parole" ("Words, Words, Words"). And my favorite word in the chapter is dietrologia, which Jones explains as follows:

As I began studying postwar Italian history, it became obvious that surrounding any crime or political event, there are always confusion, suspicion, and "the bacillus of secrecy." So much so that dietrologia has become a sort of national pastime. It means literally "behindology," or the attempt to trump even the most fanciful and contorted conspiracy theory. Dietrologia is the "critical analysis of events in an effort to detect, behind the apparent causes, true and hidden designs." [Carlo Ginzburg, The Judge and the Historian.] La Stampa has called it "the science of imagination, the culture of suspicion, the philosophy of mistrust, the technique of the double, triple, quadruple hypothesis." It's an indispensable sport for a society in which appearance very rarely begets reality.

Later in the book, Jones quotes Adriano Sofri, imprisoned for a political murder he claims not to have committed: "Dietrologia ... exalts an intricate intelligence".

The mode of reasoning in dietrologia is abduction: inference to the best explanation. Abduction is a good thing -- it's a key component of the machinery of science -- so why does abduction here lead to "fanciful and contorted" theories? There seem to be two problems:  a lack of effective coupling to the friction and inertia of fact, and an excessive value placed on indirect and even counter-intuitive explanations.

The sad fact is that science itself is sometimes subject to similar problems. And so is everyday life, even for those of us who are not convinced that the moon landings were faked or that the 9/11 attacks were staged by the CIA and the Masons. There's a well-known paper (Hobbs, Stickel, Martin and Edwards, "Interpretation as Abduction", ACL 26, 1988), which argues that

... the interpretation of a sentence is the least-cost abductive proof of the logical form of the sentence. That is, to interpret a sentence one tries to prove the logical form by using the most salient axioms and other information, exploiting the natural redundancy of discourse to minimize the size of the proof, and allowing the minimal number of consistent and plausible assumptions necessary to make the proof go through. Anaphora are resolved and predications are pragmatically strengthened as a by-product of this process.

Another approach of the same sort is Wilson and Sperber's Relevance Theory:

Relevance theory may be seen as an attempt to work out in detail [the claim] that an essential feature of most human communication, both verbal and non-verbal, is the expression and recognition of intentions [...] [This] inferential model of communication [is] an alternative to the classical code model. According to the code model, a communicator encodes her intended message into a signal, which is decoded by the audience using an identical copy of the code. According to the inferential model, a communicator provides evidence of her intention to convey a certain meaning, which is inferred by the audience on the basis of the evidence provided. An utterance is, of course, a linguistically coded piece of evidence, so that verbal comprehension involves an element of decoding. However, the linguistic meaning recovered by decoding is just one of the inputs to a non-demonstrative inference process which yields an interpretation of the speaker's meaning.

But our inferences about the beliefs, goals and intentions of others are seriously underdetermined by their actions and statements. And those of us who think we're more insightful than average may just be more imaginative. We all know people whose interpretation of communicative interaction is dietrological. Usually the "the true and hidden designs" that they infer are negative ones, amounting in extreme cases to paranoia; but sometimes the "fanciful and distorted" theories are positive ones, for example those associated with delusions like erotomania.

The trouble is, sometimes other people's intentions really do merit the evaluation of double, triple, quadruple hypotheses. But as far as I know, the practical question of how to prevent interpretive abduction from turning delusional hasn't been seriously investigated by any of the various research communities that study communicative interaction. Just aiming to "minimize the size of the proof" seems likely to overvalue behindological fantasies. Appropriate weighting by accurate prior probabilities would be one way to stay sane -- but what if such priors aren't available?

For an amusing fictional object lesson, also Italian, see "The perils of semiotic speculation" (3/14/2006).

[Hat tip to Chris Cieri for The Dark Heart of Italy.]

Posted by Mark Liberman at February 16, 2008 11:33 AM