>That is, in fact, a topic on which no one speaks with authority.

Agreed.

>Nor do I think that the impossibility of predicting the future of AI is, in itself, a reason for undue caution.

Sure.

>Bostrom is performing a sort of Pascalian blackmail by claiming that the slight chance of utter destruction merits a great deal of concern. In fact, he is no different from a long line of doomsday prophets who have evoked fictional and supposedly superior beings, ranging from deities to aliens, in order to control others. The prophet who awakens fear puts himself in a position of power, and that's what Bostrom is doing.

Consider: "Previous books published by authors hailing from Country X contained flaws in their logic; therefore since this book's author came from Country X, this book must also have a logical flaw." It's not a very strong form of argument: you might as well just read the book to see if it has logical flaws. Similarly even if a claim seems superficially similar to the kind of claim made by non-credulous people, that's far from conclusive evidence for it being an invalid claim.

It would be a shame if religious doomsayers have poisoned the well sufficiently that people never listen to anyone who is saying we should be cautious of some future event.

>And you and I both know, most if not all of those threats have turned out to be nonsense -- a waste of time.

Sure, but there have been a few like nuclear weapons that were very much not a waste of time. Again, you really have to take things on a case by case basis.

>His notion of superintelligence is based on a recursively self-improving AI that betters itself infinitely. Most technological advances follow S-curves, moving slow, fast and slow. Bostrom does not seem to grasp that, and cites very little evidence of technological change to back up his predictions about AI. He should be, first and foremost, a technological historian. But he contents himself with baseless speculation.

I can see how this could be a potentially fruitful line of reasoning and I'd encourage you to pursue it further, since the future of AI is an important topic and it deserves more people thinking carefully about it.

However, I don't see how this does much to counter what Bostrom wrote. Let's assume that AI development will follow an S-curve. This by itself doesn't give us an idea of where the upper bound is.

Estimates suggest that human neurons fire at a rate of at most 200 times per second (200 hertz). Modern chips run in the gigahertz... so the fundamental activity that chips do is being done at something like a million times the speed that the fundamental activity neurons do is being done. (Humans are able to do a ton of computation because we have lots of neurons and they fire in parallel.)

And there are lots of arguments one could make along similar lines. Human brains are limited by the size of our skulls; server farms don't have the same size limitations. Human brains are a kludge hacked together by evolution; code written for AIs has the potential to be much more elegant. We know that the algorithms the human brain is running are extremely suboptimal for basic tasks we've figured out how to replicate with computers like doing arithmetic and running numerical simulations.

Even within the narrow bounds within which humans do differ, we can see variation from village idiots to Von Neumann. Imagine a mind V' that's as inscrutable to Von Neumann as Von Neumann is to a village idiot, then imagine a mind V'' that's as inscrutable to V' as V' is to Von Neumann, etc. Given that AI makers do not need to respect the narrow bounds within which human brains differ, I don't think it would be surprising if the "upper bound" you're discussing ends up being equivalent to V with a whole bunch of prime symbols after it.