Isn’t Katja’s argument that there is an upper bound on the size of the future box? Assume that the future box is labelled “Colonize Universe”, rather than “2014″, then her great filter argument is that very few planets can ever get to the colonize box. So when SIA increases the estimated size of the 2013 box, it also reduces the estimated probability of getting from 2013 to colonize. How does the causal prior undermine this argument?
Her great filter argument does that, but it’s not a direct SIA argument—we use extra observations (the fact we don’t see other aliens) and some assumptions about similarity across different species, to get that result.
OK, so your point is that while SIA itself favours hypotheses which make the 2013 box bigger, THOSE favoured hypotheses (very large multiverse, lots of habitable planets) also tend to make the box 2014 bigger. So we don’t change the expected ratio Size(2014)/Size(2013).
It is only if we have additional evidence constraining Size(2014) - or Size(Colonize Universe) - that we get a ratio shift.
Causality means that the 2013 box being bigger makes the 2014 box bigger. If they are independent, there are many priors where making the 2013 box bigger makes the 2014 box bigger.
Katja’s argument is that SIA makes the “human-like civilization” box bigger. But observations say that the “colonise the universe” box isn’t big. Hence we can conclude that the causality breaks down between the two boxes—that human-like civilizations don’t tend to colonise the universe.
Isn’t Katja’s argument that there is an upper bound on the size of the future box? Assume that the future box is labelled “Colonize Universe”, rather than “2014″, then her great filter argument is that very few planets can ever get to the colonize box. So when SIA increases the estimated size of the 2013 box, it also reduces the estimated probability of getting from 2013 to colonize. How does the causal prior undermine this argument?
Her great filter argument does that, but it’s not a direct SIA argument—we use extra observations (the fact we don’t see other aliens) and some assumptions about similarity across different species, to get that result.
OK, so your point is that while SIA itself favours hypotheses which make the 2013 box bigger, THOSE favoured hypotheses (very large multiverse, lots of habitable planets) also tend to make the box 2014 bigger. So we don’t change the expected ratio Size(2014)/Size(2013).
It is only if we have additional evidence constraining Size(2014) - or Size(Colonize Universe) - that we get a ratio shift.
Causality means that the 2013 box being bigger makes the 2014 box bigger. If they are independent, there are many priors where making the 2013 box bigger makes the 2014 box bigger.
Katja’s argument is that SIA makes the “human-like civilization” box bigger. But observations say that the “colonise the universe” box isn’t big. Hence we can conclude that the causality breaks down between the two boxes—that human-like civilizations don’t tend to colonise the universe.
The argument is a bit more dependent on your choice of priors (see http://lesswrong.com/lw/1zj/sia_wont_doom_you/ ) but that’s the gist of it.