An argument against Quantum Immortality

In essence, quantum immortality is this: if I survive with nonzero non-one probability p after each quantum event, then in the surviving "pocket universe" I will continue to exist.  History is written by the victors, as they say.  In the same way, I exist in my pocket universe, so that bad thing that might have killed me, didn't.  In this view, no event other than one with a true zero probability of survival will wipe me out (in my pocket universe).

It's like the case of the unexpected hanging...  More on that later (maybe).

And it's like the case of the Chinese Land Grab...  More on that, later (maybe).

Old soldiers don't die, they only fade away...  More on that, later (maybe).

Here's the real problem with quantum immortality:  There is no true Identity with a capital "I".  That is, there is no invariant essence of "me-ness" that makes me me.  To put it simply, molecules are passing in and out of what I call "me" all the time, and the molecules that make "me" up are undergoing chemical reactions all the time.  Heck, they say that half the dust in a person's house is made up of his dead skin cells.  So I'm constantly changing.  

Here's an analogy: a sand dune.  Like pornography, everyone can recognize a sand dune when they see one.  Have you ever seen a time lapse photo of a sand dune?  It's really cool.  They move along the desert floor, pushed by the prevailing winds.  But here's the really cool thing: the sand dune is made up of completely different grains of sand from one day, week, year, to the next.  Like old soldiers, sand dunes don't ever die.  They fade away.

So what if a sand dune had a 10% chance of being vaporized in any given universe each day?  But then what if it had a 100% chance of eventually fading away, in every universe?  Would the sand dune (if it were sentient) ever be able to claim immortality?  I say no, because at some time before it fades away, it ceases to be *recognizable* as itself.

My claim is the same thing happens to humans, in all their pocket universes.  Like old soldiers, we fade away.

Quantum immortality is like the unexpected hanging in this way: It's guaranteed for sure that you'll lose your ability to function as a sentient human some time in the next 1000 years, just due to "old age".  But you'll never see it coming, that's a promise.  So, you'll reason that it can't be on the last day, right?  Or you would see it coming.  So by that reasoning, it can't happen on the 2nd-to-last day, etc, etc.  One day, though, in *each* pocket universe, you will cease to be recognizable to yourself or anyone else as you.  Bam!  (as Emeril would say) you've been unexpectedly hanged.

Quantum immortality is like the Chinese Land Grab.  Quite honestly, I don't know if that's the right name for it (I don't want to cast aspersions on the Chinese, but I was told by an actual Chinese person that this is a Chinese folk story), but it goes like this.  A powerful landlord has given a tenant farmer a plot of land to use to feed himself and his family.  One day, the landlord simply moves the fence, depriving his tenant of 20 feet of land.  The tenant is upset, but it's not worth fighting over just 20 feet.  This happens again, and again.  Each time, it's not worth fighting.  Eventually, the tenant has no land at all.  This is how an individual ceases to exist, too, not necessarily all at once, but little by little.  And in each pocket universe, it's *inevitable.*


An interlocutor objects: Within the context of Many Worlds I think that all seems pretty reasonable.  I'm not sure why the lack of me-ness is a problem necessarily, though.

Graeme's answer: The lack of "me-ness" strikes at the heart of quantum immortality because quantum immortality depends on a surviving "me" in some pocket universe after every event.  However, if the "me" fades away in every pocket universe, like a sand dune that has been gradually flattened by the wind, then there's no "me" to survive forever.  The "me" ceases to exist at some random but finite time in the future, and as in the unexpected hanging, "me" find this (unpleasantly) surprising.

Interlocutor: Quantum immortality is an artifact of the Many Worlds interpretation.  It's interesting to consider, but I don't take it too seriously either. 

In any event, you were describing a sequence of events that have a probability between zero and one of resulting in the death of the individual.  This isn't consistent with the individual eventually being dead in 100% of the universes in a finite number of such events.  The partition of universes that still contain a living "me" will decay exponentially with time, but it will only become empty in the limit of an infinite number of such events.

I don't think a continuous sense of self is necessary for quantum immortality; only an observer with a memory (or record).  I.e. the many worlds interpretation doesn't describe or assume any sort of essence.

I can also think of ways to escape biological senescence, such as encoding my consciousness in a different type of hardware.  So, within the context of quantum immortality, I might claim that some sort of persistent existence might be possible arbitrarily far into the future.

Quantum immortality actually seems like the (weak) anthropic principle applied to individuals.  Unfortunately, both are basically untestable conjectures.

In terms of likelihood, I agree that senescence and death are the safe bets.

Graeme replies: Regarding your comment, "This [sequence of events with 0<p<1] isn't consistent with the individual eventually being dead in 100% of the universes in a finite number of such events," I totally agree.  My view is that the "me-ness" of the individual is what fades over time (due, as you say, to biological senescence), and eventually becomes so "not me" that the "me" is certainly gone by any measure.  You put your finger on this problem -- and some possible solutions -- with your suggestions of ways to escape biological senescence.  The point I'm making, and which you seem to appreciate as well, is that my "me-ness" is not on or off -- one or zero -- but, like a sand dune, gradually ceases to be itself without any instant in time that one can point to where it happened.  So the thing ("me") that can be said to have quantum immortality also can be said to have slipped away somehow.  

Interlocutor: I agree. This "me" that we are talking about isn't really very well defined.  I would venture to say that objectively there is no such thing as "me".