# The First Person And The Physical Person

*This is another attempt to promote my approach to anthropic paradoxes. I framed the argument differently hopefully making it more clear. Please refer to* [*my website*](https://www.sleepingbeautyproblem.com/) *for more.*

What "I" Means
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In the strict indexical sense, "I" just means the first person. However we also often interpret it as the physical person uttering the word and usually equate the two meanings, "I am this physical person" after all. But there is a caveat. The equivalency is bound by the perspective. 

The first person meaning of "I" is restricted to its own viewpoint, from other perspectives only the physical meaning can be used. If I hear you say "I'm hungry", to me the only correct way of interpreting it would be the physical person "\[insert reader name\] is hungry", not that "I am hungry" (as in "dadadarren is hungry"). We do this sort of transcoding naturally all the time. 

What's more subtle is this should also apply to "god's eye view" (or "view from nowhere" if you prefer). If we try to be objective and reason from a god's eye view, then we shouldn't be using the first-person "I" at all. For it would only refer to the imaginary impartial observer, not any particular person. 

But we keep using the two meanings interchangeably in anthropic problems. Effectively jumping back and forth between our natural viewpoints and the god's eye view. This is the cause of paradoxes and why different camps have trouble communicating.

Is "I exist" Meaningful Evidence?
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One major contention in anthropics is whether or not "I exist" can be used as evidence to support certain theories. (Which exact theory, such as more observers, big universe, or ["fine-tuning"](https://www.lesswrong.com/posts/R9QkdCeLkeqW34TSz/hello-ordinary-folks-i-m-the-chosen-one-1) is a separate matter. ) One camp suggests it does not support any theory because "I would always find myself exist". The other camp disagrees arguing that is claiming "My existence is guaranteed to happen". Which is obviously untrue. So "I exist" is valid evidence. Both camps are unconvinced by the opponent's argument.

The key difference between the two camps is they are using different meanings of "I". When the former argues "I would always find myself exist", they are using the strictly indexical, first-person meaning of "I". i.e. No matter whose perspective we choose to take, we will always conclude the first person exists. It does not have any specific physical person in mind. 

On the contrary, when the opponents say 'I exist' is not guaranteed. They are using the other interpretation. Here it is not about the first-person, but that specific physical human being. A particular person's existence is of course not guaranteed, so it shall be considered new information. This argument is taking a god's eye view instead. 

Against SSA
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To cut to the chase: I think "I exist" is not valid evidence. The first-person interpretation above is right, while the physical interpretation has some missing links. 

But before getting into it, I want to clear a common misconception: that "I always find myself exist" is an argument based on [SSA](https://www.lesswrong.com/tag/self-sampling-assumption). That is not true. It is a very simple conclusion once we keep to the first person meaning of "I". SSA is an additional assumption carefully made to not contradict it. Nevertheless, SSA is ultimately wrong.

Let's look at this in the context of the Doomsday Argument. It claims once considering my birth rank among all humans, the rational forecast of our species' future population shall be greatly reduced. Because I am more likely to be a typical person, aka, to be considered as a randomly selected sample from all human beings. 

Doomsday Argument does not consider "I exist" as evidence. So it is using the first-person sense of "I" here. From a first-person perspective, the basic logic of the forecast is as follows: "At the very start, I realize I am this physical being. Then I find out there are other similar physical beings. Let's call all these similar things "human".  Some humans are born before me, others after. I want to make a rational estimate of how many will come after me." 

Notice in the above analysis there is no place for the uncertainty of "among all human beings, which one is me?". "I'm this one" is evident right from the beginning. What the Doomsday Argument does is take a god's eye view, look at all human beings impartially, then raise the question "among all these people which one is me(I)?". But from the god's eye view, the first person meaning of "I" is not usable. Some additional thing is needed to complete the logic. So SSA specifies a physical person by random sampling, then *assumes* that particular person is equivalent to the first-person "I". 

This assumption lacks any rational backing whatsoever. It misguides us to use the indexical "I" and that physical person interchangeably. It conceals the random jump between the first-person perspective and the god's eye view in reasoning. And eventually leads to the paradoxical conclusion. 

What About SIA?
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How about we consider "I exist" as valid evidence? As mentioned before, that means it is interpreting the statement by the physical person. In the case of the Doomsday Argument for example, "I exist" would suggest a greater number of humans. 

But there is a missing link. Why update the belief about the world based on this particular physical person's existence? Why not do so based on someone else's existence/nonexistence? 

For example, why say "Since \[insert reader name\] exists there are probably more observers than it seems?" instead of saying "Since Obama's son does not exist there are probably fewer observers?" What justifies this kind of special attention to that particular person?

The most intuitive response would be "Because I am that particular person". Of course, I shall give it special attention. But, this response is actually using the first-person meaning of "I". If one endorses this use, then "I exist" would always be true therefore cannot confirm any theory. Here it needs an explanation that can be used from a god's eye view instead of the first-person "I". 

This is where [SIA](https://www.lesswrong.com/tag/self-indication-assumption) kicks in. It assumes the first person "I" is equivalent to the physical observer selected by random sampling. The sampling process is constructed so the sample's existence is evidence for more observers (e.g. a random sample from all *potential* observers). This makes the probability update using "I exist" as evidence feasible. 

Consequently, this also means all the criticisms against SSA above - lack of rational backing, allows the interchanging use of the indexical and physical person, etc - also stand for SIA. 

Anthropics Is NOT About Observer Selection Effect
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SSA and SIA's similarities matter far more than their discrepancies. The only difference is, SSA's sampling process is constructed so that it does not affect the assessment of "I exist" while SIA does. In a sense, SIA makes more errors yet it is more consistent. It applies to all probability operations while SSA only applies to parts. Yet substituting the first-person "I" with a random sample is where both mistakes lie. 

Anthropic problems are special because they are formulated using specific first-person perspectives. (This is more obvious in the sleeping beauty problem. "when you wake up in the experiment". The awakening being questioned is identified by beauty's first-person experience with indexical concepts such as "now" or "today" instead of any objective measure) Using observer selection effects such as SSA or SIA to substitute the indexicals and solve it from a god's eye view is a misguided attempt due to habit. They shall be solved by thinking from that perspective in question. Doing so means there's no uncertainty such as "which observer is the first person I". The first person has no reference class nor can it be regarded as some random selection outcome.