Toby—interesting essay. But I’m struggling to find any rational or emotive force in your argument that ‘strong longtermism tells us to look at the set of possible theories about the world, pick the one in which the future is largest, and, if it is large enough, act as if that theory were true’
The problem is that this leads to a couple of weird edge cases.
First, if we live in a ‘quantum multiverse’, in which there are quadrillions of time-lines branching off every microsecond into new universes, then the future is very very large indeed, but any decisions we make to influence it seem irrelevant, insofar as we’d make any possible decision in some branching time-line.
Second, the largest possible futures seem associated more with infinite religious afterlives than with scientifically plausible theories. Should ‘strong longtermists’ simply adopt Christian metaphysics, on the assumption that an infinite afterlife in heaven would be really cool, compared to any atheist metaphysics?
Thanks for the comment! I have quite a few thoughts on that:
First, the intention of this post was to criticize strong longtermism by showing that it has some seemingly ridiculous implications. So in that sense, I completely agree that the sentence you picked out has some weird edge cases. That’s exactly the claim I wanted to make! I also want to claim that you can’t reject these weird edge cases without also rejecting the core logic of strong longtermism that tells us to give enormous priority to longterm considerations.
The second thing to say though is that I wanted to exclude infinite value cases from the discussion, and I think both of your examples probably come under that. The reason for this is not that infinite value cases are not also problematic for strong longtermism (they really are!) but strong longtermists have already adapted their point of view in light of this. In Nick Beckstead’s thesis, he says that in infinite value cases, the usual expected utility maximization framework should not apply. That’s fair enough. If I want to criticize strong longtermists, I should criticize what they actually believe, not a strawman, so I stuck to examples containing very large (but finite) value in this post.
The third and final thought I have is a specific comment on your quantum multiverse case. If we’d make any possible decision in any branch, does that really mean that none of our decisions have any relevance? This seems like a fundamentally different type of argument to the Pascal’s wager-type arguments that this post relates to, in that I think this objection would apply to any decision framework, not just EV maximization. If you’re going to make all the decisions anyway, why does any decision matter? But you still might make the right decision on more branches than you make the wrong decision, and so my feeling is that this objection has no more force than the objection that in a deterministic universe, none of our decisions have relevance because the outcome is pre-determined. I don’t think determinism should be problematic for decision theory, so I don’t think the many-worlds interpretation of quantum mechanics should be either.
Toby—interesting essay. But I’m struggling to find any rational or emotive force in your argument that ‘strong longtermism tells us to look at the set of possible theories about the world, pick the one in which the future is largest, and, if it is large enough, act as if that theory were true’
The problem is that this leads to a couple of weird edge cases.
First, if we live in a ‘quantum multiverse’, in which there are quadrillions of time-lines branching off every microsecond into new universes, then the future is very very large indeed, but any decisions we make to influence it seem irrelevant, insofar as we’d make any possible decision in some branching time-line.
Second, the largest possible futures seem associated more with infinite religious afterlives than with scientifically plausible theories. Should ‘strong longtermists’ simply adopt Christian metaphysics, on the assumption that an infinite afterlife in heaven would be really cool, compared to any atheist metaphysics?
I’d welcome any thoughts about these examples.
Thanks for the comment! I have quite a few thoughts on that:
First, the intention of this post was to criticize strong longtermism by showing that it has some seemingly ridiculous implications. So in that sense, I completely agree that the sentence you picked out has some weird edge cases. That’s exactly the claim I wanted to make! I also want to claim that you can’t reject these weird edge cases without also rejecting the core logic of strong longtermism that tells us to give enormous priority to longterm considerations.
The second thing to say though is that I wanted to exclude infinite value cases from the discussion, and I think both of your examples probably come under that. The reason for this is not that infinite value cases are not also problematic for strong longtermism (they really are!) but strong longtermists have already adapted their point of view in light of this. In Nick Beckstead’s thesis, he says that in infinite value cases, the usual expected utility maximization framework should not apply. That’s fair enough. If I want to criticize strong longtermists, I should criticize what they actually believe, not a strawman, so I stuck to examples containing very large (but finite) value in this post.
The third and final thought I have is a specific comment on your quantum multiverse case. If we’d make any possible decision in any branch, does that really mean that none of our decisions have any relevance? This seems like a fundamentally different type of argument to the Pascal’s wager-type arguments that this post relates to, in that I think this objection would apply to any decision framework, not just EV maximization. If you’re going to make all the decisions anyway, why does any decision matter? But you still might make the right decision on more branches than you make the wrong decision, and so my feeling is that this objection has no more force than the objection that in a deterministic universe, none of our decisions have relevance because the outcome is pre-determined. I don’t think determinism should be problematic for decision theory, so I don’t think the many-worlds interpretation of quantum mechanics should be either.