The point of his argument, if I understand correctly, is that we should expect a bubonic plague in the future to be more of an x-risk than it was in the past, because our past evidence is filtered by anthropic considerations. And because his argument isn't in any way specific to the plague, he will expect x-risks in general to be more prevalent in the future.
However, I don't understand how to quantify this. How much should I update towards the next bubonic plague being an x-risk? A little? A lot?
The historical plague could have wiped out humanity, but for anthropic reasons. And also, the flu of 1918 could have wiped out humanity, but for anthropic reasons. And the flu virus created recently in the lab could have escaped and wiped out humanity, but didn't, for anthropic reasons. And also I have in my garage the pestilent bacterium Draco invisibilis, and if it ever infects a human, we are all doomed; but it never has, for anthropic reasons...
I have just finished reading the section on anthropic bias in Nassim Taleb's book, The Black Swan. In general, the book is interesting to compare to the sort of things I read on Less Wrong; its message is largely very similar, except less Bayesian (and therefore less formal-- at times slightly anti-formal, arguing against misleading math).
Two points concerning anthropic weirdness.
First:
If we win the lottery, should we really conclude that we live in a holodeck (or some such)? From real-life anthropic weirdness:
It seems to me that the right way of approaching the question is: before buying the lottery ticket, what belief-forming strategy would we prefer ourselves to have? (Ignore the issue of why we buy the ticket, of course.) Or, slightly different: what advice would you give to other people (for example, if you're writing a book on rationality that might be widely read)?
"Common sense" says that it would be quite silly to start believing some strange theory, just because I win the lottery. However, Bayes says that if we assign greater than 10-8 prior probability to "strange" explanations of getting a winning lottery ticket, then we should prefer them. In fact, we may want to buy a lottery ticket to test those theories! (This would be a very sensible test, which would strongly tend to give the right result.)
However, as a society, we would not want lottery-winners to go crazy. Therefore, we would not want to give the advice "if you win, you should massively update your probabilities".
(This is similar to the idea that we might be persuaded to defect in Prisoner's Dilemma if we are maximizing our personal utility, but if we are giving advice about rationality to other people, we should advise them that cooperating is the optimal strategy. In a somewhat unjustified leap, I suppose we should take the advice we would give to others in such matters. But I suppose that position is already widely accepted here.)
On the other hand, if we were in a position to give advice to people who might really be living in a simulation, it would suddenly be good advice!
Second:
Taleb discusses an interesting example of anthropic bias:
You'll have to read the chapter if you want to know exactly what "argument" is being discussed, but the general point is (hopefully) clear from this passage. If an event was a necessary prerequisite for our existence, then we should not take our survival of that event as evidence for a high probability of survival of such events. If we remember surviving a car crash, we should not take that to increase our estimates for surviving a car crash. (Instead, we should look at other car crashes.)
This conclusion is somewhat troubling (as Taleb admits). It means that the past is fundamentally different from the future! The past will be a relatively "safe" place, where every event has led to our survival. The future is alien and unforgiving. As is said in the story The Hero With A Thousand Chances:
Now, Taleb is saying that we are that hero. Scary, right?
On the other hand, it seems reasonable to be skeptical of a view which presents difficulties generalizing from the past to the future. So. Any opinions?