Over the past several decades, various multiverse proposals have been gaining a lot of traction. Eternal inflation, for example, posits that we are one of a potentially infinite number of island universes floating in a sea of space. This is all very exciting, but there are some unfortunate ethical problems for us if it turns out to be true. The ethical theory of consequentialism, in particular, might need a pretty big overhaul.
The problem stems from the idea of infinity. If there are an infinite number of universes, then this suggests that all possibilities, no matter how unlikely, are actualized an infinite number of times. Why? Well, imagine that you are playing poker and about to be dealt a hand of cards. You’re considering the odds of receiving a royal flush: 0.000154%. Very low indeed. But what if, instead of being dealt only one hand, you are dealt an infinite number of hands? Well, then your probability of receiving a royal flush increases infinitely. In other words, if you were able to examine all of your hands, you would find an infinite number of royal flushes. In fact, you would also find an infinite number of other hands – some good, some bad, but with an infinite amount of hands, you will find among them an infinite amount of every possible hand.
This manifests itself in an infinite multiverse in the following way: every possible universe will exist and there will be an infinite number of each. That not only means that each of us has an infinite number of twins with the exact same thoughts, feelings, and memories, but each of us also has an infinite number of saintly twins, an infinite number of evil twins, an infinite number of bald twins, an infinite number of cross-eyed twins, etc. etc. There are also an infinite number of universes where there are civilizations just like ours, or nothing like ours, or no civilizations at all. I don’t want to beat a dead horse, but this point needs to be driven home. Any possible universe, no matter how improbable, will exist and be infinitely numerous.
If you subscribe to a consequentialist system of ethics, then you’re in trouble. In The Moral Landscape, for example, Sam Harris posits a consequentialism based on “well-being.” Whatever increases the well-being of sentient creatures, says Harris, is “good.” That which decreases the well-being of sentient creatures is “bad” or “evil.” But, as John Barrow points out in The Infinite Book (Pg. 172), there is a big problem:
If the total amount of good (or evil) in the Universe [or Multiverse] is infinite, then nothing we can do (or fail to do) can add to it: infinity plus anything is still just infinite. … If ethical imperatives are based simply upon doing more good things, then they make no sense in an infinite universe [or infinite Multiverse].
This is a big puzzle for me because consequentialist ethics seem to make the most logical sense (to me, at least) in a world where good and evil are finite quantities. But how can we make sense of this if good and evil are both infinite quantities? In fact, it seems that most philanthropic enterprises might be doomed as well. For example, if your goal is to reduce the number of AIDS cases in Africa, what would you make of the fact that there are an infinite number of Africas? There would be an infinite number of AIDS cases, and nothing you do would ever put a dent in that total!
It is possible to come up with a solution by elevating the importance of our world, but this seems arbitrary. We would need something much better than that if any of these mutliverse proposals is experimentally verified.