Re: Leslie's "The End of the World"

Robin Hanson (
Fri, 14 Aug 1998 10:59:06 -0700

Nick B. writes:
>> Say you knew that all intelligence was either bio or
>> postbio, with bio intel living for days to decades, and postbio intel living
>> from thousands to billions of years. Then you expect that conditional on
>> being a bio intel, you are typical, so bio intel shouldn't last much more than
>> a few decades more (assuming continued exponential growth). And conditional
>> on being a postbio intel, you know you must be one of the very first
>Why? If being a postbio intel is all you conditionalize on, this
>doesn't follow. If I knew nothing except that I was a postbio intel,
>I wouldn't expect to be one of the very first; I would expect to be
>one of the middle 95%.

I meant that since I am a bio now, the only way I could be a postbio as well is if I am one of the transitionary people who is both at different times in their lives. And transitionary postbios are the first postbios.

>> And without introducing more info, you couldn't say much about
>> your chances of being postbio vs. bio intel.
>If postbio and bio intelligences all belong to the same reference
>class (just as tall people and short people, black and white etc.)
>then the fact that you find yourself being a bio intel. would
>indicate that the postbios don't vastly outnumber the bios.
>Whether postbios and bios should be in the same reference class is
>not clear. That's a deep problem, and I suspect but am not yet
>certain that there might be some kind of loophole for the
>transhumanist here, if the postbios are fundamentally different from

I reread Leslies book on this issue last night, and object to putting bios and postbios into the same ref class in exactly the way that Leslie envisions one might object:

It might perhaps be complained that making the reference class into humans-after-splitting-away-from-Neanderthals would be coming too near to imitating the man who makes his reference class into people-born-as-late-as-himself-or-later [p. 261, The End of the World]

>... Of course, the exact conclusion depends on how you estimate
>future population figures etc., but in general I see the DA as, so
>to speak, *superimposed* on whatever other evidence you might have.

If you do a Bayesian analysis of all your information carefully, the DA effect will be embodied in your analysis, and should not need to be added in seperately.

I'm now reading your paper on the DA, and hope to write a summary of my opinions on DA soon.

Robin Hanson RWJF Health Policy Scholar, Sch. of Public Health 510-643-1884 140 Warren Hall, UC Berkeley, CA 94720-7360 FAX: 510-643-2627