>I know I have some particular set of experiences. If there were fewer people, then while there might be someone having the experiences I’m having, it’s less likely that my particular experiences would be had by me.

Isn't this false in general, and thus in need of greater qualification? Suppose God flips a coin: if heads, he creates a thousand people and randomly assigns ten a red jacket and the rest blue jackets; if tails, he just creates one person with a red jacket. I notice my jacket is red. This is obviously going to be evidence for the tails outcome (since observing blue would be definitive evidence for the heads outcome), in spite of the fact that fewer people with my experience of seeing a red jacket exist on tails.

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But your existence is a necessary fact. It is metaphysically impossible for you not to exist, because the act of calculating the probability of your own existence comes only after your own existence has been established.

This is entirely distinguishable from contraception because contraception doesn’t impact the probability of whether you exist, it impacts the probability of you being a flesh and blood human whose body was created by sexual reproduction. The changes of you specifically existing in some form are always 100%.

Saying that it’s about your own experiences is also not relevant. If you exist, maybe you will have some arbitrary set of experiences, but since you’re guaranteed to exist, having some arbitrary set of experiences doesn’t predict anything. The chances of you having this are 100% either way.

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I know that I do, in fact, exist. That doesn't mean it's metaphysically necessary that I exist. That's obviously false--there's a possible world where I don't.

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As far as you’re concerned, those worlds don’t exist, because you aren’t around to reason in them.

Also, don’t you believe that SIA requires that every possible world contain every possible being?

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A world can exist even if I don't exist in it!

//Also, don’t you believe that SIA requires that every possible world contain every possible being?//

No, what?

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My existence is metaphysically necessary???? This does not follow from the fact that I know that I exist being used as part of my background knowledge for Bayesian analysis. This reasoning would mean that if I rolled a 100-sided die and it landed on 50 six times in a row and I start calculating the probability of this event given the hypothesis that it is a weighted die vs a fair die, suddenly there’s a 100% metaphysically necessary chance that this extremely unlikely event occurred and I’m not allowed to determine that the die is probably rigged. That’s absurd.

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What? That doesn't follow at all. There's a 100% chance of you existing on any theory. I.E. if the Universe were made of balloons and you were to calclate the probability of you existing, the probability would be 100%, because the fact that you're doing the calculating means you exist.

This is *not* because "I exist" is being used as "background" to the Bayesian analysis. Even if you entirely failed to account for your own existence in a Bayesian analysis, the chances of you existing would be 100%. You are the one performing the analysis!

In contrast, it is entirely possible for you to calculate the probabilities of a dice rolling suspicious numbers without depending on the dice rolling a specific set of numbers. I am not saying that something is "metaphysically necessary" just because it in fact happened!

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I’m a little confused about what you’re saying. You said “the probability would be 100%, because the fact that you're doing the calculating means you exist.”

Let’s say that God rolled a 100-sided dice 6 times and would only create me if it came up 50 every time. Couldn’t I then say “the dice coming up 50 6 times in a row is metaphysically necessary because the fact that I’m doing the calculating means that the dice came up 50 6 times in a row”. This reasoning is obviously flawed and it appears to be exactly the same as what you’re saying.

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1. No. My whole point is that the proposition “God would only create you if [X]” is nonsense. Your existence is necessary, it *cannot* be conditioned on anything. You as an observer must always exist because if you don’t exist then nothing else does—your consciousness mediates anything else that can possibly exist.

So I would say that the antecedent is senseless. If God can overcome what is metaphysically necessary, then you can’t blame the resulting illogic on me.

2. If God did roll such a dice and created you, then that wouldn’t necessary only be evidence that the dice were rigged. Maybe he rolled many many times.

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I’m still really confused about how you’re getting to this view that my existence is necessary in the first place. I can see that given that I am experiencing things, my existence is necessary, but that’s only conditional necessity. You’re suggesting that it is a matter of simple necessity that I simply must exist.

What leads you to this view? You say “if you don’t exist then nothing else does - are you a solipsist?

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As Bulldog has laid out the evidence, Solipsism is the best hypothesis, yes.

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> Here’s one way that makes good sense if you believe in souls

I agree that SIA makes sense if souls existed, but this is not a point in favor of SIA. If you require to postulate non-physical entities to make sense of your probability theory application, it seems that you've made a few wrong steps along the way.

> Suppose that I’m considering two hypotheses. Both predict that there are two people in a room. One of them predicts that both of them will, when they look under a table see a red strip of tape, while the other theory predicts that one of the two people will see a red strip and the other a blue strip.

This is a great example. Let's explore it in more details.

Suppose that you are none of these people. However, there is some mechanism that tells you about what one of these people observed. Let's say that there is a red light in your room. And you know that if the light goes on it means that a red strip was observed. But you are not sure about the actual algorithm. Does the red light just always goes on because there is always a person who observes a red strip? Or does it sometimes goes on because of it, and sometimes it doesn't, regardless of whether there are two red strips or not? Or does the red light correspond to the particular person and specifically when this person observes the red strip it goes on and when this person doesn't observe a red strip it doesn't? If it's the latter, can this person possibly not observe the red strip? Are strips assigned to people at random and a random person observation of the red strip leads to red light going on? Or is the person who gets assigned the red strips is also always the person whose observation of it leads to turning the red light on?

In other words, either observation of red light is not correlated with any of two hyposthesises or it is. You've observed one of these events:

1. "At least one person has observed a red strip" or you observe event

2. "A person who always observe a red strip has observed a red strip"

3. "A person who could have not observed a red strip has observed a red strip"

According to conservation of expected evidence you are not supposed to update in 1 and 2 but you are supposed to update in 3.

The problem is that you can't a priori deduce whether you observed 1, 2 or 3. The same universe that allows you to observe 3 can just as well let you observe 1 and 2. And so to simply commit to treat all the situations the same way, without inquiring about the specifics of the causal mechanism is a clear mistake. And this is why SIA is wrong in a general case.

> Upon finding this out that the raspberry exists, you get evidence for theories on which there are more raspberries.

Suppose that there are two theories. That there are 100 raspberries in a bag or that there are 1000 raspberries in a bag. You are given a particular raspberry from a bag. You don't actually update in favor of there being more raspberries in a bag, do you?

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The point about souls was mostly a way of getting a handle on SIA's picture of reality. It doesn't require actual belief in souls. Though, if it did, that would be fine because souls do exist https://benthams.substack.com/p/you-are-a-soul

Re red strip, the evidence is that I, in particular, saw a red strip, and there's only one red strip I can see.

//Suppose that there are two theories. That there are 100 raspberries in a bag or that there are 1000 raspberries in a bag. You are given a particular raspberry from a bag. You don't actually update in favor of there being more raspberries in a bag, do you?//

No because that raspberry doesn't have the property of being such that if it exists I'd know and if it doesn't I wouldn't.

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> It doesn't require actual belief in souls.

I agree that there are other possible options but my point still stands. Just as you can critique SSA for appealing to solipsist intuitions you can critique SIA for appealing to dualist intuitions. The theories get penalties if solipsism/dualism are wrong.

> Though, if it did, that would be fine because souls do exist

I've read your post about souls and didn't find any of it persuading. Some arguments, such as mind swaps, survival after the death of the body and the possibility of having two minds, that you bring in favor of souls sounds to me as actually penalizing the souls hypothesis - no one observed any of this things happening and abscense of evidence is evidence of abscence.

In general, yes, the existence of souls would fit with our naive intuitions of mind/body dualism and personal identity - that's how we came up with the concept of souls in the first place - but as we learnt about the workings of our universe it became clear that these intuitions are flawed.

> Re red strip, the evidence is that I, in particular, saw a red strip, and there's only one red strip I can see.

I feel that you didn't engage with the setting at all.

> No because that raspberry doesn't have the property of being such that if it exists I'd know and if it doesn't I wouldn't.

Interesting. So what have to be changed about the raspberries so that you should have updated?

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Does SIA suggest that I should accept a form of panpsychism where the universe is packed with consciousnesses experiencing exactly what I'm experiencing? It seems to suggest a vast infinity of consciousnesses exactly like mine, perhaps one at every point in space.

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That theory is better all else equal, but starts to look very improbable in that it says you are probably an atom, when your experiences don't seem like an atom's experiences (they're too complicated). A better theory, I think, is one on which all possible people exist--and then it doesn't matter where you put them. Theism, I think, nicely explains why every possible person might exist.

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Mar 25·edited Mar 25

Still, doesn't SIA make me incredibly sure that I'm an atom on priors? To the point where I'd require some truly huge amount of counterevidence to overcome such a prior. Probably more than I can accumulate through all my life?

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Bulldog SIA actually supplies an infinite amount of evidence in favor of you being a disembodied entity, because according to Bulldog, SIA implies that an unboundedly large number of people exist. Even more people than the size of the set of all posible truths.

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SIA gives you reason to think infinite beings exist, but it tells you nothing about what they are.

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(It seems like the problem of trapped priors.) There's no reason to assume anything if you wake up in a room. Sure, you might wake up with crazy beliefs (priors) and then you can conclude anything. But that's not a great argument for this (meta)strategy.

> alternatives to SIA don’t really treat your existence as something that you update on

Which distribution you would need to update? Was your existence so underestimated previously, that you need to update on it? Your existence is already part of your prior(s), and when you notice it, there's no delta. No new information.

When you look around you update on the existence of things you see, that you can move your head, the experience of changing viewpoint (moving).

And sure, experiencing things should make us consider that there might be other beings with experience (but we don't know anything about how similar/different theirs might be).

And thus upon encountering strange questions about possible worlds ... we can use a Bayesian approach, but our prior is consistent with both versions to exactly the same degree, hence we have to conclude that both are equally likely theorems/scenarios. (This might be the only room, we might be the randomly picked lone A, and so on. [And it doesn't matter if we know that if God were to iterate the setup we would exist in 5/6 of the cases, because we don't have data about this. Sure we might be living in a simulation, if we assume a world where that's likely. But that's just failing Ochkam.])

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The fact that there are people who deny SIA shows that some philosopher or other will defend any kind of insane view.

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I think you're very right that, if you have some sort of essentialist model of personhood wherein everyone is most basically a soul or something similar, then a lot of metaphysical objections to the SIA are not problematic. But if you don't take that view, then I think there's a plausible story for the SSA that makes a lot of sense. I also think the concern about reference classes is overblown - it doesn't seem weird to me that we would be unsure about whether a particular entity is someone "you could have been," and it might even be an empirical question.

Finally, I'd just say that there is a sense in which the SSA'er updates on their existence, right? When you find that you exist, you narrow down the worlds you're considering to those in which you exist and you don't consider the ones in which you don't. That's the narrative that makes sense to me. You're basically saying, "Hey, it turns out I exist, so however many people exist, I'm one of them" and then you go on to think about all the different possible worlds where that's true. This is why I don't get the "why do you think you would be created in any world?" objection - it's not that I think I'm guaranteed to exist in any world that gets created, but just that, from my own existence, I know those worlds can't possibly be actual so why would I consider them?

(Also, Joe Carlsmith has a sorta funny mystical explanation for the SSA in his big piece, if you remember, and honestly I think someone could take that and run with it if they really wanted to because 1) it's kinda cool and 2) I still think it's more plausible than infinitely many people actually existing.)

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