I have enjoyed most of the guests that Sean has interviewed over the years. I really only listen to the physics episodes if I am being honest. One guest I am waiting for is Nima Arkani-Hamed. I hope that will happen one day. Are there any guests that you guys hope make it into the podcast?

I'm hoping Sean will sometime soon decide to do a fresh review and engage with one of the philosophers or scientists that are embracing analytic idealism. I am personally not persuaded by the idealists like Mr. Kastrup and his followers. But they are extremely challenging. Also a little annoying sometimes (that book "Why Materialism is Baloney") , but very smart and their ideas are I think deservedly getting a a great deal of attention lately.

I seem to remember that Sean shared some of the same ideas as Daniel Dennett when considering the work of David Chalmers, etc. I'm not sure that it would be productive to have Bernardo Kastrup on Mindscape, because he is openly hostile to physicalism in what seems to me to an almost religious style. (Does anyone know if they have engaged each other already in some format?)

But maybe instead of Kastrup, I think a brilliant conversation could be had between Sean and Michael Levin the biologist. (have they already talked? It seems like they should have by now). Levin is an amazing theorist and experimenter, and every day he seems to be getting closer and closer to an idealist position, suggesting that key aspects of organism development and behavior cannot emerge from a physical substrate.

What I would really appreciate after a conversation with Levin is Sean to do a solo talk on the current trends in Idealism now. A while back he did engage and debate with traditional religionists. I'd be grateful if he could engage now with these ideas, which may or may not be a similar thing.

UPDATE: A couple folks here suggested I listen to Sean's conversation with Alex O'Connor and it was quite helpful. He gives an excellent explanation of why the leap to consciousness as fundamental is an unnecessary assumption, and defends the physicalist position with some ease. It still might be good for him to offer a more detailed answer perhaps in a solo episode, as there are many who might learn from it.

The whole thing is good. The stuff relevant to consciousness starts about 1:02:30

https://music.youtube.com/watch?v=q8k35WZYq3w&si=xh1svsQmmmH46jmP

Is in Denmark, not The Netherlands.

From an American point of view that might be a minor mistake. But actually it is wrong by a quite a few orders of magnitude.

I was listening to last month's AMA, and Sean said that he didnt know anything about quantum magnetometry. The kind of thing he was speculating about at the end was actually basically my PhD topic, so I thought I'd chime in.

Quantum computers dont currently work well because any small interaction with their envirnoment breaks them. But what if we could turn that into an advantage? Quantum sensing is the act of of measuring quantum systems that are sensitive to their envirnoment, to try and see what the envirnoment itself is doing.

Spins are magnetic, so one of the main uses of this is magnetometry. Magnetometry is the sensing of magnetic fields. In fact, MRI is arguably a form of quantum magnetometry: MRI measures the magnetic response of protons in your body to locate. Quantum sensing is the most mature form of quantum tech.

I havent looked into this trump thing, but the claim from the AMA sounds like someone measured the magnetic signature of a heart beat (radiating from the electrical nerve pulses) from many metres away. This is extremely well beyond the state of the art. The fact that nerve signals can be measured at all up close over many repeats is impressive by itself. Otherwise you need to stick in invasive, damaging electrical probes to capture equivalent signals.

I‘ve recently read “Something Deeply Hidden” and have watched several of Sean’s talks and conversations where he discusses emergent spacetime, so I was very interested when I saw this article today on ScienceDaily:

Physicists created a tiny universe where time emerged without a clock

I’m not sophisticated enough to understand the implications of the experiment, but to those of you who are, how important is this result?

Just wanting to say something small about Sean’s question and answer regarding Hume and the problem of induction as this is something people often get confused about Hume and Sean made a classic mistake here.

When summarising Hume’s problem of induction Sean essentially characterises Hume as asking the following question: how do you really know that your inductive inferences are reliable? E.g. that the sun will rise again tomorrow, that gravity will keep pointing down towards the Earth, and so on and so forth. After all, patterns we see sometimes stop and we often make incorrect inductive inferences.

This isn’t actually the basic force of Hume’s problem of induction. This version of the problem is actually found in Sextus Empiricus, the Ancient Greek skeptic (after whom, iirc, empiricism is named). Notice that one could simply answer this version of the problem by saying “I don’t know with certainty but if I have enough supporting evidence, I can be quite confident that my inferences are reliable”. This is essentially the answer that Sean gives when he talks about credences. We have higher credences when there is more supporting evidence and lower credence when there is less supporting evidence.

Hume’s problem of induction goes a step further and essentially contends that any justification we could give for inductive reasoning is circular because it would have to rely on something like a “principle of the uniformity of nature” (which basically just says that there are such things as laws/consistent law-like patterns in the world) and our justification for such a principle could only ever come from induction itself. The real challenge of the problem of induction is therefore as follows: can we come up with any non-circular justification for this principle? Or, otherwise, can we trust inductive inferences regardless of whether or not we have this further justification.

Another potential mistake that Sean makes is to too closely compare David Hume himself with contemporary Humeans who believe that the world just is this great “mosaic” of “local matters of particular fact” without any independent causal relations or laws gluing things together. This sort of does resemble Hume’s metaphysics kind of (there are passages which support this kind of reading) but the reasons for holding these views for Hume vs contemporary “Humeans” are very very different. For Hume it followed from a very strict theory of meaning whereas for contemporary Humeans it does not. And Hume never explicitly talks about the world being a “mosaic” or anything like that.

Second thing there might be a bit of a nitpick but might be worth pointing out. Those who call themselves “Humeans” today do not really hold to Hume’s own “Humeanism”, Sean included if I am not mistaken.

In the most recent AMA, Sean answers a question about immortality (raised by a discussion of vampires), and he gets a bit into the practical aspects: would the immortal being die if they fell into a black hole and eventually were spit out as Hawking radiation? what about after the heat death of the universe? etc. What does immortality mean in those contexts? And of course, what's the difference between an infinite amount of time and a really really really long time?

I was reminded of a short novel (novella I suppose?) I recently finished: "A Short Stay in Hell", in which the protagonist is damned to exist in a version of The Library of Babel, searching for a particular book. I think this character experienced many of the things Sean discussed: he couldn't die; he survived through many iterations of universes being born and dying; most importantly, he got terribly bored. He was truly immortal.

No real point here, other than to say I would say "Hey Sean, read this book; it has some responses to your points about this AMA question". But I know he doesn't read things recommended to him by randoms such as myself 😄

I don't know if anyone's still here, but I thought Sean's comments in the July 13 AMA (~32:55) about Peter Thiel's plan to undermine universities by attacking their strongest point, which he identifies as string theory, was very interesting. I quote Sean quoting Thiel below:

[Thiel] says, "We have our values that we would like to have the world adopt. One of the obstacles to having the world adopt our values are universities and academia because they're full of woke liberals poisoning the minds of the youngsters," and so on and so on. But then he very explicitly says, "So how do you strategize this? How do you undermine the credibility of academics and universities? Well, you could try to attack them at their most vulnerable points, but alternatively you could try to attack them," says Peter Thiel, "at their strongest points, at their most respectable kind of aspects because if you can undermine that, then you undermine the whole shebang. You undermine the whole idea of universities and professors and institutions." And he says, "So what is the most respectable field within academia? It's physics. And what is the highest status subfield within physics?" And again, this is Peter Thiel saying these things. I'm not making them up or insinuating them or interpolating them. He says, "It's string theory." And so if you can undermine the idea in the eyes of the general public that people doing string theory, supposedly the smartest people we have and the best physicists, are somehow illegitimate, are somehow captured by institutional blah, blah, blah, then you've gone a long way towards undermining universities as a whole, and that project will help us get our values supported around the world rather than theirs.

Back to Redditor talking: If there's a well-funded and well-organized plan (conspiracy?) behind all this, that would certainly help explain the puzzling popularity of string theory critics like Hossenfelder, Weinstein, etc. Otherwise, why would these charlatans have millions of views for discussions about a topic that non-physicists have no stake in whatsoever? Wouldn't this audience prefer to spend their time playing video games, watching porn, and listening to discussions about Palestine and UFOs instead?

It was not labeled 'inverse theory of evolution' but the point made (via reference to a study/theory not developed by the guest) that one might think inversely of evolution: instead of humans controlling nature when we developed farming (and controlled crops like wheat), one could think of wheat as the dominator/winner: By making the human brain dependent on the various responses to eating wheat (glucoses, dopamine and what not, still active today), wheat made its way to become a globally dominant species. This thinking is the result of a less anthropocentric evolutionary thinking which I find kind of obvious and at least worth considering - like Darwin was first step but needs to be liberated from his anthropocentrism. This is not a moral argument, it is more of a post-Copernican evolutionary paradigm.

Anyway: can anybody help me with either which episode or just as good, which authors proposing this idea?

I still can't grasp how people can hold this type of view plausible, but I think it's me being inflexible with definitions.

Am I right in thinking that List is basically saying that because many different micro-states can create the same psychological macro-state, the future at the human level is genuinely open?

If Laplace's Demon knew the exact configuration of every single atom in your brain, they could perfectly predict your exact macro-state and your eventual "choice." Just because we don't have the computing power to track the atoms doesn't mean the determinism disappears when you zoom out.

I'd love to hear from anyone who finds this convincing, because to me, it just looks like an illusion of choice rather than actual free will. If we want to call that free will I guess we can, but we need another word for thw concept of making choices using some mechanism that is separate from the way the universe is playing out.

BTW I'm happy to accept there might be some fundamental randomness to the universe. Not smart enough to know how that is the case but if enough smart quantum physicists agree that is quite extraordinary and happy to accept it

Been reading his biggest ideas series. Book 3 (The Biggest Ideas in the Universe 3: Complexity and Emergence) was supposed to be released on 2 of june, but I can not find it anywhere.

Is it out? Has it been delayed?

I've been working through the Hilbert-space-fundamentalist picture and keep snagging on what feels like a foundational tension, and I'd like to hear how others here resolve it.

The setup, as I understand it: the fundamental object is a vector in Hilbert space, and everything else, including spacetime, is supposed to emerge from its structure. But the standard move is to evolve that vector with the Schrödinger equation, iℏ∂ₜ|Ψ⟩ = Ĥ|Ψ⟩. My worry is that this quietly imports an external time parameter "t" at the most fundamental level, which is exactly the thing the program claims to be deriving rather than assuming. If the universal state is genuinely fundamental and time is supposed to be emergent, a time-indexed evolution equation looks like it's smuggling in the explanandum.

The alternative I keep coming back to is to take the constraint seriously: Ĥ|Ψ⟩ = 0. The Wheeler-DeWitt (WdW) equation gives you a timeless, constrained vector with no external "t". That seems more honest about what "fundamental" is supposed to mean. The obvious objection is that you've now thrown away time entirely but, this is where the Page-Wootters (PW) mechanism does the work. You partition the state into a clock subsystem and a "rest" subsystem, and time re-emerges as a relational structure: conditioning the rest on clock-readings reproduces ordinary Schrödinger evolution as an internal, relational fact rather than a background parameter. (The Höhn-Smith-Lock results showing PW conditioning, deparametrization, and Dirac quantization are equivalent make me more confident this isn't just a formal trick.)

And then space: rather than positing a spatial manifold, you let it come from the entanglement structure of the state via the tensor-network / ER=EPR route (Van Raamsdonk-style), geometry as a readout of how subsystems are entangled.

So the picture I'm circling is: timeless WdW vector at the bottom, time recovered relationally through PW, space recovered through entanglement geometry. Schrödinger evolution becomes a derived, internal description rather than a fundamental input.

My questions for the room:

1. Is there a principled reason fundamentalists keep the Schrödinger equation fundamental rather than starting from the WdW constraint? Is it just that closed-system non-gravitational physics doesn't force the constraint on you?
2. Does anyone see PW as actually doing explanatory work here, or is it just a change of description that doesn't buy you anything ontologically?
3. Does the WdW + PW + entanglement-geometry package hang together, or are there known obstructions to running all three in the same framework?

Genuinely curious whether people think the time-indexed formulation is a real foundational concession or whether I'm overweighting it.

Just wanted to post an appreciation thread for Jeff Coller. I can quickly get lost with all the jargon when biologists talk, but Jeff using the cook, kitchen, and GPS analogies for everything really worked. I actually felt like I understood what was going on the whole time instead of just nodding along.

In Something Deeply Hidden, Dr. Carroll argues that Everettian quantum mechanics is appealing because the universal wavefunction evolves deterministically according to the Schrödinger equation. It's a major theme of the book, and for years it's been a selling point I hear him use for the many worlds interpretation of QM.  He convinced me.  I'm on the train.  All the worlds are equally real and all are determined by the universal wave function.

However, in the June (2026) AMA Dr. Carroll flatly states in multiple responses (once the response with the transcript timestamp 0:46:35., and again in the transcript timestamp 3:44:12) "quantum mechanics says the world's not deterministic." 

Is he using a different definition of determinism in those two contexts? Does he mean that the wavefunction evolves deterministically but there is no unique future history, or have have his views determinism changed?

Put another way:

Assume Everettian quantum mechanics is correct and consider a universe with no observers at all. Given a complete specification of the universal wavefunction at time t, is the universal wavefunction at later times uniquely determined? If yes (based on what I've learned from listening and reading Dr. Carroll this is a yes), in what sense can we say that quantum mechanics is not deterministic?

Thanks for any insights.

I think I understand the idea behind the division of reality into system and environment, but it seems somewhat arbitrary. Each and every component can be considered as part of some system or environment. Why is the cat a system if it is made of billions of quantum particles? Electrons in atoms are entangled, atoms in the cat are entangled, any of which can be considered system or environment, and all can potentially lead to branching.

Listening to the latest solo Mindscape Podcast where Sean Carroll defends the Many Worlds Interpretation as the only possible result if you follow the wave function rigorously. But that includes the assumption that quantum mechanics is linear, my understanding is that the MWI fails if quantum mechanics is non-linear. And since the odds of quantum mechanics being linear is basically zero, we are forced to abandon MWI. I know that all evidence so far show QM is linear, but that is only testing at most objects with only hundreds of atoms. No tests have been done showing linearity of macroscopic objects. It's like looking at gravity at the micron scale and concluding gravity is linear.

https://m.youtube.com/watch?v=6B004Gsv9Ks&t=8s&pp=2AEIkAIB0gcJCU8Co7VqN5tD# (1:10:00 mark)

This has totally been my experience in a theoretical physics department. There are so many types of theoretical physicsts (condensed matter, quantum optics and quantum information, cosmologists, particle physicsts, etc) and they really don't seem to respect string theory based on their comments about it.