I'm then questioning his suggestion that we can dismiss the conclusion that we are most likely Boltzmann brains a priori, as that then entails that we can dismiss some empirically well-supported scientific model a priori. For example, as per RogueAI's comment above, one supposed solution is to dismiss (4) a priori. Is that really rational? — Michael

Yup. From what we have seen of quantum fluctuations, we know that's a possibility, given enough time? — Patterner

If our scientific models entail that we are most likely Boltzmann brains, and if our scientific models are correct, then we are most likely Boltzmann brains.

If our scientific models entail that we are most likely Boltzmann brains, and if we are not most likely Boltzmann brains, then our scientific models are incorrect. — Michael

Yup. From what we have seen of quantum fluctuations, we know that's a possibility, given enough time?
— Patterner

I'm not sure how we could say we know that. — wonderer1

If we are most likely BBs... — Janus

Not we. It's just me. The rest of you are false memories. — Patterner

Talking as if memories are distinct entities, things that can be stored, seems mistaken to me. — creativesoul

That's just something programmed into my false memories. — Patterner

Memories are stored, are they not? In the brain, in some physical manner. — Patterner

No, that is a false memory of some knowledge you imagined you had. — Janus

the point being that we cannot coherently use scientific theories to draw the conclusion that we are most likely BBs — Janus

How many virtual particles have been observed in the same place at the same time? — Patterner

The thing is that virtual particles are not observed. — Lionino

Well, whatever way it is that we know they exist. — Patterner

Does that seem rational? Or is it just more rational than accepting the possibility that we are most likely Boltzmann brains? — Michael

Talking as if memories are distinct entities, things that can be stored, seems mistaken to me.
— creativesoul
Memories are stored, are they not? In the brain, in some physical manner. — Patterner

We accept that heat death and eternal expansion will happen, we accept that quantum fluctuations will form significantly more Boltzmann brains than normal observers have ever existed, but we don't accept that we are most likely one of these Boltzmann brains. Although I'm unsure how to justify this. — Michael

That is a possible argument against solipsism, that all the body of knowledge produced so far is generated/contained by/in my mind, and yet we struggled with Abstract Algebra 2. — Lionino

but it works, in my view, because I redefine mind to exclude involuntary aspects. It works because it satisfactorily counters solipsism in its semantics. It does not defeat idealism or pan-psychism or open individualism or a blend of all those, because the world could still be fundamentally made of mind-stuff, or we and the world are the mind of god a la Spinoza — Lionino

I tried looking up some educative articles on the matter but none of them were complete. If it is in your interest, you can try. In any case, the short answer is that you can have as many "particles" as you want, it is simply less likely the more particles you want to have.

Your objection is roughly that we need a great number of particles before making a brain, that is something that was discussed starting here. — Lionino

Virtual particles are just mathematical tools for calculations of particle interactions. They only exist on paper - they cannot be observed in nature.

Furthermore, virtual particles are exactly the same particles as "normal matter" particles. Virtual particles are just normal particles that we artificially add to interactions when using a calculation method called perturbation theory.

Virtual particles do not necessarily carry the same mass as the corresponding ordinary particle, although they always conserve energy and momentum.

Vacuum fluctuations appear as virtual particles, which are always created in particle–antiparticle pairs.

B: There are things in the world I am not aware of. — Lionino

B: There are things in the world I am not aware of.
C: Therefore there are things outside of my mind. — Lionino

Which is that there is scientific knowledge to be learned, the fact I don't have this knowledge implies there are some things that I am not aware of, therefore there are things outside of my mind. There is some X I am unaware of, X is outside of my mind, there are things outside of my mind. But this only works because the implication {unaware of X} → {X outside of mind} is accepted, and it can be assumed only if we define my mind in such a way (A) to rule out the existence of some unknown-to-me part of my mind. A semantic argument therefore. — Lionino

If virtual particles did manage to form a BB, I have to wonder if the different mass would affect the brain's functioning. — Patterner

Could this be an implication of accepting the Kantian thing-in-itself in empirical world? — Corvus

Kant never denied the existence of material things.
[...]
By referring to the ‘something’ that affects our sensibility and, hence, produces representations, Kant follows what he elsewhere terms Locke’s physiology of the human understanding (cf. A IX). Yet he goes on to note that we do not have to conceive of the ‘something’ that underlies appearances as a material object. It might as well be considered as something that is immaterial and can only be thought.
[...]
As we will see, Kant accepts the Leibnizian view that a non-material something must be considered to underlie appearances. Yet he does not identify the latter with the ‘something’ that is said to affect our sensibility
[from a footnote]
Jacobi implicitly identifies both the terms ‘transcendental object’ and ‘thing in itself’ with material objects that exist independently of the subject, something that in my view is not warranted. — Kant’s Multi-Layered Conception of Things in Themselves

Or does it mean just there are things that you have no experience of, therefore no awareness of them? — Corvus

Yes, you have given out your reason for the conclusion, but I am not sure if a semantic argument would be enough evidence for the ground. Because your language reflects the content of your mind, but not the other way around i.e. your belief is not based on what you said. — Corvus

Virtual pair particles are entangled, which does not mean necessarily that they will be right next to each other — Lionino

(whatever that means) — Lionino

I, personally, don't think we are Boltzmann brains physically speaking... — Lionino

I think the Ding an sich is an epistemological being, not an ontological one. — Lionino

But that is the matter of whether the Ding an sich is ideal or double or monadic or material or whatever. Whether the noumenon is automatically an outside world, whether mental or physical, is another question. Since the very idea of noumenon assumes of a world besides the perception of a transcendental agent, it would make sense that without the noumenon there is nothing to perceive. I think the semantics of Vorstellung pretty much imply an outside world, so solipsism implies no Vorstellung. Coming up with a view in which there are things outside of perception and yet solipsism obtain seems to be a contradiction of the semantics of solipsism.

So to answer your question, yes. — Lionino

a quick introspection shows there are things in my mind whose origin I don't know — Lionino

How could something be an epistemic being — Corvus

If you accept the existence of the Kantian Thing-in-itself in Noumena, then that would be a proof of the existence of the outside world. No? Because Noumena exists in the physical or external world. — Corvus

In the transcendental argument of the Refutation of Idealism, Kant’s target is not Humean skepticism about the applicability of a priori concepts, but rather Cartesian skepticism about the external world

More specifically, Kant intends to refute what he calls problematic idealism, according to which the existence of objects outside us in space is “doubtful and indemonstrable” (B274)

All off the above from the SEP.

It cannot exist in your mind according to Kant, or do you believe it does exist in your mind? — Corvus

For example, what are they? What are the things that you find in your mind whose origin you don't know? — Corvus

I am not persuaded by Kant's argument. — Lionino

Some folks seem to believe that the Thing-in-itself exists in the mind. — Corvus

If you accept the existence of the Kantian Thing-in-itself in Noumena, — Corvus

But I imagine that for Kant the noumenon is always outside of the mind, and to prove the existence of a noumenon is to disprove solipsism.
Solipsists would have to deny noumenons. — Lionino

Some folks seem to believe that the Thing-in-itself exists in the mind.
— Corvus

It is defined as otherwise. So thats incoherent. — AmadeusD

The Noumena is not hte thing-in-itself. It is the existent as perceived by something other than human sense-perception. So, unknown to us, but theoretically knowable. The Ding-en-sich is that existent without any perception of it is my understanding.

So perhaps it (the argument of Kant) is not being adequately outlined. — AmadeusD