[venus]

I think you're misunderstanding what a "black swan" event is supposed to be. It's not just something that is unpredictable; that is normal. It's something that is so outside the whole frame of reference that it wasn't even not predicted; its very existence destroys the entire framework used to make the predictions.

In that sense, although your definition was wrong, you're actually kind of right - the reason predictions so often fail is that they do not take into account the unknown, which is basically a tautology, though one probably worth repeating since it's so hard for our brains to actually accept.

[001sky]

No, he's right both historically and logically.

History: a black swan was rare to a european. but it was native to australia. the idea labeleing events 'black swans' only makes sense in the context of the story being told from the european perspective, not the anitpodean.

Logically: A black swan is an ebodiment of non-stochastic process or the intrusion of factors outside the stochastic process under consideration. ie, its about uncertainty not risk/probability. the parametrics of risk/probability are therefore irrelevant, in the normal sense (ie, as priors or ex-ante odds, etc). It is equally as non-sensical to call a black swan x or y probability.

TLDR - A black swan is more akin to something from outside the known-state-space. [1]

[1] see also: http://en.wikipedia.org/wiki/Knightian_uncertainty

[001sky]

In case you doubt this (as comment above was downvoted), it would be interesting to hear your logic/analysis.[1]

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[1] Wiki: The phrase "black swan" derives from a Latin expression; its oldest known occurrence is the poet Juvenal's characterization of something being "rara avis in terris nigroque simillima cygno" ("a rare bird in the lands, very much like a black swan") (6.165).[3]

In English, when the phrase was coined, the black swan was presumed not to exist. ...

Juvenal's phrase was a common expression in 16th century London as a statement of impossibility. The London expression derives from the Old World presumption that all swans must be white because all historical records of swans reported that they had white feathers.[4] In that context, a black swan was impossible or at least nonexistent.

After Dutch explorer Willem de Vlamingh discovered black swans in Western Australia in 1697,[5] ....

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So, if you are an Australian the idea of a black swan was completely different (one of a known variety, like a kangaroo vs a wallaby) to the historical use in "the west" (ie, europe/rome/england). The 'Idea' as its used with respect to statistics, now has an Idiomatic meaning, that is not the Australian one, but rather based on the European experience.