In a striking excerpt from his book about living among the Pirahã, which it would really improve this blogpost to improve but I don't want to spend time finding, linguist and missionary Dan Everett notes that the Pirahã were difficult to convert to Christianity because they would believe things they'd seen, and things others' would say they had seen, but no further. So if Dan told them he had seen Jesus, they would believe him; but if Dan told them he read an account of a guy who had seen Jesus, they would say "ah, what do you know!". For the same reason, they had no creation myth at all (after all, it happened far too long ago for anyone alive to have seen it!).

The natural reaction— well, actually, I guess the natural reaction to this story is to think "huh; ain't that something". Maybe find it funny. Perhaps frustrating, if you're a missionary. But, after that, I think it occurs to (non-Pirahã) people that the Pirahã seem to be violating something we might call "testimonial closure". After all, if Mr A telling us X is good evidence of X, and Mr B telling us X is good evidence of X, in general, then Mr A telling us Mr B told him X should be good evidence of X, right?

Well, yes and no. Examples abound on both sides. For instance, recursive testimony is how we know anything about the wider world at all. History, science, and so forth, all probably rely on this mechanism (think back to how you learned, even, say, the names of countries you've never been to!). However, it seems like people are TOO credulous about testimony-of-testimony. This is, I think, at least one reason why hearsay is banned in a court of law. Urban legends and factoids spread constantly, all based on hearing someone tell you that he heard a thing from someone else. Destructive gossip. Religion (or, at least, all of the false religions, presumably, whatever you think those are).

Which obviously brings to mind Hume's argument against miracles. This is one of the greatest arguments in philosophy because it counters a natural human flaw of credulity with the incredible power of calm human rationality. "Which is more likely," asks Hume (to paraphrase): "that an extremely infinitesimally unlikely thing happened (counter to all of our previous experience), or that someone was mistaken (which happens all the time)?". I'm personally a somewhat credulous person, that is to say I err on the side of believing people, so this argument has even an emotional weight to me. I can feel the emotional/instinctual conviction that people must be telling me the actual truth... somehow... crash headlong into Hume's gentle reminder that someone being confused is a fairly ordinary event.

Anyway, the Pirahã have an in-built application of Hume's argument against miracles in their epistemics, a built-in defense against recursive hearsay. It's a little too strong; they don't know... almost anything at all. But among the peoples of the earth, they may hold the distinction of believing the fewest FALSE things, or having a pretty good truth-to-falseness RATIO, and that's pretty notable (if it is, in fact, true).

Another interesting fact is that the Pirahã believe in, like, spirits/demons, but they also have personal experiences of seeing these spirits, but also the spirits just look like animals, people, or locations(?) that are possessed in some way. It's weird, idk.

It doesn't escape my notice that in this blogpost lightly condemning recursive testimony, I am citing the account of a guy who saw some things——— so maybe I should believe him, but you shouldn't believe me!