During Nebula reading I ran across several stories that explored the Many Worlds Interpretation of Quantum Theory.
The Many Worlds Interpretation addresses the idea that our universe is merely one of infinitely many possible universes, and that for everything that happens in our universe, there exists a universe somewhere in which something different happened. It's a fairly common theme in science fiction right now, possibly because the theory is new and shiny and begs to be played with.
I'm all for playing with new, shiny things. But so far, Many Worlds stories leave me with a vague dissatisfaction. This is not because the stories are badly executed -- they aren't! -- but because I simply can't get my brain to accept the validity of the interpretation.
If, for every me that got cancer, there is also a me who didn't...
And if for every me who is happily married to my husband there is also a me who divorced him...
And if for every choice I make, there exists a me who made the opposite choice...
Then not only is free will an illusion, but it is also irrelvent. The Many Worlds Interpretation, as frequently utilized in fiction, implies that agency means nothing, and that ludicrous worlds exist in which ludicrous combinations of decisions pile on top of each other. By that logic, there must exist, somewhere, a universe in which I spent my morning eating a flavor of ice cream I despise while standing on my head in the center of the living room. In some other universe, I am contemplating suicide. In some other universe, I am a murderer.
My brain recoils at this idea. In a very real sense, my identity is nothing more than the sum of my decisions. To claim that I have never really made any decisions, that all apparent decisions were really just an effect of the eternally branching nature of existence, is to claim that I have no identity.
But it gets worse. If we postulate that the Many Worlds Interpretation is correct, then I cannot take joy in anything good that happens me. How can I take pleasure in prosperity when hundreds of thousands of other me's languish in poverty? Conversely, if I have just been beaten and robbed, I am not at all consoled by the knowledge that an infinite number of me's have been spared this atrocity.
The Many Worlds Interpretation robs me of all joy when life goes well and does not ease my pain when life is hard. It denies agency and steals my identity.
And that is why I do not like it.