> There are plenty of real, non-physical things. ... Think about, oh, say, a road. What's the difference between a road and a random patch of asphalt? ... There is the world of ideas. Things held in the mind, in the consciousness of people have real-world effects on the physical world around us. ...

Indeed, and Music may be the most prominent example of that!

It's basically a bunch of things inducing vibrations in a physical medium. To other beings that noise may very well be no more meaningful than static on our television screens, if they can even hear in those frequencies, let alone be able to pick out the different instruments used in a piece.

We have built an entire industry and a sub-universe of knowledge around it. Rules, notation, tools, a system of writing it down, and recording it and sharing it. People gain celebrity through it and are remembered for their achievements in it.

Music is one of the best example of things that exist only in our heads and still profoundly effect OUR world.

Now just imagine an alien species that, for example, can sense their planet's magnetic fields in the same detail that we sense sound waves. Imagine them making their "music" by manipulating those fields. They could have an entire culture and industry around it, a sub-universe that would be practically meaningless if not completely invisible to us.

It's amusing to think about, really. A person getting rich and fame for finding creative ways to manipulate air vibrations in certain patterns, because these patterns give some special sorts of mental tingles to people who experience them.

Oh don't stop there. He's rich because of these little pieces of paper that, for some reason, are so valuable you can remove the physical artifact of pieces of paper and represent them solely with bits in a computer system.

And fame? How in the world would you connect that to the physical?

> just imagine an alien species that, for example, can sense their planet's magnetic fields

Radio?

>many more things in existence are non-physical than physical.

What does non-physical existence even mean? This isn't an idle question. Surely we know what physical existence is: some capacity to interact; be causally affected or causally affect other physical things. This definition is a bit circular in some sense, but it has closure which is important.

The word "exist" has a foundational importance in all of human intellectual activity. What is the analogous notion of non-physical existence that supports it sharing this term?

>If consciousness itself were something on the same order as an idea, then it would lose none of its potency.

When we say consciousness exists, we're not saying something of similar importance of how a child might say giant pink elephants exist. They're both ideas, but we mean something very different.

> What does non-physical existence even mean? This isn't an idle question

Much of modern life exists by convention only (by agreement among people) and has no physical existence. Bank balances, ownership of property, no-parking zones, national borders, having a college degree, the prestige level of a school, friendship, being a Seahawks fan, agreements, the law, political affiliation, religion, etc.

But all those things have an "ontology" (mode of existence) owing to being constituted by or supervening on things we know to exist (carbon, hydrogen, electrons, etc). These things are abstractions, but ultimately are grounded in physical existence either by the instantiating substance or substances that operate on the abstraction (e.g. brains). But those who argue for non-physical existence of things such as numbers are going further than this by saying that these non-physical entities are independently members of the constitutive fabric of the universe. This seems entirely unsupported and unnecessary.

The concept of existence seems to require conscious observers.

Sure, inasmuch as concepts require conscious minds. But surely the universe would exist if it had never spawned conscious observers. So I don't see that the question of existence begins and ends with conscious observers.

It has to begin and end with conscious observers, because they are the only ones that can consider the question. The universe does not need your answer, you do. The question quite literally ends when you do.

Why? Did universe not exist before the first life appeared?

The meaning of the word "exist" implies that it has some way to be detected by conscious observers.

Consider this: if I tell you there about a parallel universe you can never detect or discover, how does saying "BUT IT EXISTS" differ from saying "GOT YOU, IT DOESNT EXIST"?

I get your hypothetical example, however, will the universe cease to exist after the last conscious observer dies? For that observer, one minute before their death, would/should they suppose that universe will cease to exist or continue existing?

If we humans manage to wipe out ourselves next year in a nuclear holocaust, then is the continued existence of our planet conditional on some other conscious life arising in the future? Obviously it continues to exist even in your definition because they would be able to observe it, but how could such life arise if the universe doesn't exist?

I'd rather define "exist" as having an effect on our physical reality, which would obviously be detectable by "observers" in e.g. the quantum mechanic meaning of "observation" that has no relation to consciousness.

You're focusing too hard on the "existence" part and not hard enough on the "thing" part.

If humanity died tomorrow, nobody would be around to call the planet "Earth". Earth is merely a concept held in the minds of people. The concept consists of properties, only some of which involve the physical aspects. For example, lots of other planets are physically present, but only one we call Earth, because we live on it. Should we not live on it anymore, why would anyone bother to call it by a name.

In that sense, sure, Earth would cease to exist if we stopped living on it.

The problem with defining existence as only involving the physical is that it yields a world in which nobody can make sense of anything. You can't simply boil everything down like that and actually live in that world. The very second you started thinking, you'd start ascribing properties to objects that aren't merely physical, recreating the entire debate.

Before you consider existence, think about what "thing" means.

You said it yourself: "having an effect on our physical reality". It is a binary relation: something exists because we can experience it or deduce it from other things we experience.

In your hypothetical example, the existence a planet after it has eg exited our visible universe (because of the rapid expansion of the universe) is only relevant to us because we were able to deduce it from previous observations. Same with things in the past. So to answer your question, since we observe the Earth now, we can deduce its continued existence even after a cataclysm that would wipe out all life on Earth. We could be wrong in our extrapolation. Maybe the Earth would be hit by an asteroid later and things would be different in a way no one imagined. But, without conscious observers at that point, that state of affairs would be not unlike physics in that parallel universe. In that case, according to your definition, it wouldn't exist.

All of these are implemented in specific patterns that actually exist in reality and are detected by the brain.

> The word "exist" has a foundational importance in all of human intellectual activity.

Are you sure about that? I have a personal mental exercise / thought experiment where I try to iterate on my understanding of what it means to exist. But I wouldn't call that foundational. I maybe run through it once a month or so. Certainly it's attained a great deal of importance, but really, iterating on my understanding is never going to really get me anywhere.

Anything can be said to "exist". If you are thinking about it, it's currently existing in your mind as thought. If you're not thinking about it, but have thought about it in the past, then it exists in your memory. If you've never thought about it, then it's a potential that you could experience someday. It could also exist as a potential quantum state that nothing living could ever consider.

I'm reminded of the "library" where every possible grouping of characters is tied together with a math function and you can search for whatever you want. Considering whether everything ever written 'exists' or not just kinda lost its thunder to me. If everything meets some criteria, then it's the criteria that needs to be examined, not the everything. Archimedes wanted to move the world with his lever, but really, it's way more interesting to just move half.

You'd have to somehow escape your own mind before you could truly consider something that doesn't exist somewhere.

I don't think existence, in that sense, is as big of an idea as people seem to think. The way I usually use it is to get at the fundamental quality of being human. I think about agency, goals, limitations, purpose. These things seem way more interesting than trying to drive at the fundamentals of everything.

What it means for me to exist is way cooler to think about than what it means for my bed to exist.

I'm perfectly fine with this deflationary concept of existence, and leave the "foundational importance" to particular kinds of existence that actually warrant it. Once its articulated like this I have no problem. But my problem is with those who want to speak of existence of abstract objects in terms that claim such entities are independently members of the constitutive fabric of the universe. I just have no idea what this kind of existence means.

Your definition of physical existence above is not circular in some sense, it is circular in any sense since you define physical existence in terms of interacting with other physical existence. Just to test your definition, are colour or sound physically existent in your definition?

It's "in some sense" because we're defining the physical in terms of causal closure, rather than explaining the true nature of the physical (i.e. what physical matter supervenes on).

>are colour or sound physically existent in your definition?

Hard to answer without first having some kind of theory of mind. If we take the mind to be solely comprised of physical matter then mental states are particular organizations of that matter. Color and sound being mental states/percepts, they would be particular abstractions of physical matter. The abstraction itself would have no physical existence.

I am not sure I get your definition of causal closure. Would "black is what looks the same colour when put next to a black item" qualify as a causal closure, and if yes how can that be a non purely self referential definition in any sense? On colour and sound, how do you separate between the physical representation of the abstraction and the abstraction itself? You seem to be approaching a causal closure of non-physical existence, though one I am not sure is right.

The purpose of a definition is to pick out only those instances of a set you're attempting to refer to. The set of objects subject to causal influence by members of the set is well-defined and unique. Your example with black doesn't work because there are multiple non-intersecting sets that satisfy the critera, so we need some further conceptual machinery to distinguish them.

>You seem to be approaching a causal closure of non-physical existence, though one I am not sure is right.

I'm not sure I follow. To be clear, the "causal closure" was referring to the fact that the physical is subject to causation, rather than a generic term describing a set of self-similar items.

> They're both ideas, but we mean something very different.

are you sure about that?. words are a social convention adopted to provide a vehicle for transferring meanings from one mind to another. what are the meanings underlying the words though? why do you agree that the conventional word "idea" can be used to signify both meanings, but then claim that the meaning is somehow very different.

>why do you agree that the conventional word "idea" can be used to signify both meanings, but then claim that the meaning is somehow very different.

Well I can only go by how the words are used. But when we're speaking rigorously, such ambiguities matter. The issue is that there are multiple ways these words are used. But when we try to use the casual meaning in more rigorous contexts, the discrepancies are important. When it comes to existence, people are purporting that there is an existence completely unlike physical existence, yet retains its centrality in our conception of the world and its constituents. I'm looking for clarity here. If we can't flesh out the nature of non-physical existence, we should refrain from using the term "exists" in those contexts.

ambiguity is an inescapable consequence of systems of communication based on social convention. That's really the fundamental reason why physicists have such a strong preference for mathematics. The convention there is of logic and notation rather than social preference and personal idiosyncrasy as with natural language.

but we don't have the means to use a rigorous system of communication when discussing consciousness. there is no calculus of mind. its not even clear that there could be, in principle.

so we need to re-calibrate our notion of rigor and precision to deal with the domain we're working in here. we shouldn't just wring our hands and lament that our communication tools fail us. we can still use them, we simply need to be more disciplined and avoid devolving into arguments about language semantics and conventions and try to focus on the actual content, ambiguous as it may seem.

here's a simple working definition of "existence" that may be ambiguous but should hopefully not be controversial. a thing exists if it is experienced by a conscious mind. this includes material things which are experienced via the conventional senses (sight, hearing, etc.). it also includes immaterial things, such as thoughts and ideas, which are experienced internally within a conscious mind.

this definition does not resolve the ambiguity regarding the point-of-origin of immaterial things, but that is not particularly relevant in my opinion. we don't need to answer that question in order to engage with the material, so let's just leave it unanswered.

> What does non physical existence even mean?

It's a faulty concept. Everything is physical. But I think it refers to non-material aspects of the physical, especially patterns of cause and effect.

> There are plenty of real, non-physical things. Evolution is real, and non-physical, you can describe it using mathematical formulas. Math decides how the real world happens.

Math is an invention of man it doesn't exist in the real world. There is matter and energy and they interact. Quantities of stuff exist but there are no numbers. That is extrapolation and modeling with man-made tools. Math decides nothing as it is not a fundamental aspect of reality.

> Math is an invention of man it doesn't exist in the real world

I see this from time to time, and certainly opinions can differ, but I tend to cringe when I see this idea pushed. From my perspective, math is not an invention of man, but a discovery. Math is an intrinsic part of the universe, that we continue to discover and piece together. Certainly we have invented the symbols and the terminology, but the underlying concepts...these laws, these truths exist whether we discover them or not, whether we give them names or not.

I'd say that's debatable. My admittedly limited understanding of mathematics is that the underlying truths that emerge depend on the axioms in play. My understanding of axioms is that of 'rules' to the mathematical games we play, and you can change which rules you follow and get different results.

https://en.m.wikipedia.org/wiki/Axiom

https://en.m.wikipedia.org/wiki/List_of_axioms

If we accept that in mathematics we're finding out about the outcomes of the rules we choose to follow, then I have no problem in thinking of mathematical discoveries as truths, but I'd say they are conditional truths rather than absolute truths. What are your thoughts on this?

Right, but there are things like surreal numbers that feel more like constructs- useful, interesting and so forth, but not discovered in the real world so much as a tool built out of available materials.

Math dances along the edge between discovery and invention.

> there are things like surreal numbers that feel more like constructs

The fabric of the physical realm usually doesn't care about anyone's feelings.

> but not discovered in the real world so much as a tool built out of available materials

The fallacy here is that you assign different valuation between discovering a thing through observation, and discovery through thinking.

For example, the Higgs boson was conjectured many years before it was first observed. Following your argument, I could argue that the Higgs boson was invented by us.

What's true is that we made up the Higgs boson, but that didn't change the unobserved existence of it. In the same way, we may have made up surreal numbers, but that doesn't discard the possibility of their unobserved existence out there somewhere.

The Higgs fell out of math that was originally designed to model the world. It was a testable prediction of a physical theory. The math could have been wrong. The math probably is wrong, except about other things than the Higgs.

I'm not valuing anything. I'm saying that if I build a toy axiomatic system, there's no reason a priori to believe that it resembles anything in the physical world. Such a system (say, Peano arithmetic) doesn't actually make any predictions about the real world at all, and cannot be falsified scientifically.

It's like saying, I painted a picture of a dog, therefore I have discovered a dog, by proving that it could exist. Except your depiction is of a 100-foot-tall mecha-dog that definitely doesn't exist. Mathematics is sometimes (though by no means all or most of the time) more like painting than it is like science.

Ex: the Banach-Tarski paradox is almost certainly not describing anything physical.

Amen. Well-stated.

Are there non-physical things? I doubt it.

Let's take the road. Obviously the mass of the road itself (the object) is physical and has physical characteristics like its components, the chemical composition of its components, the elements in the chemicals, the particles and forces in the atoms of the elements, etc.

Now let's take the idea of a road. Where does that idea actually reside? In the brains of living beings, which are themselves physical.

Ideas are information, and information is physical. You need energy to create and maintain it, and it can be quantified in terms of the entropy spent to create it. It is a persistent pattern of mass/energy.

The "world of information" only seems infinite to us because we are so inefficient at working with it outside each of our own minds. Think of the incredible amount of mass and energy that must be expended to create a road, or even a book, or even an SD card. By contrast, our 8 lb. lump of brain stores and returns vast quantities of information with seemingly no effort on our part.

But of course thinking does require physical effort. An inert human, thinking in a chair, still requires food.

The problem with this line of thought is that it completely upends classical cause and effect. Things have effects in proportion to their size. The sun has a way bigger effect on us than Jupiter does.

But when you get to the scale of ideas, the logic upends. The pen should not be mightier than the sword, but is because ideas have outsized effects on the world compared to their physical size as merely electrons moving in brains.

But logic can be maintained by extending existence out to the non-physical. Ideas can be bigger than other ideas, and you can logically evaluate them. You just have to figure out the rules first.

The pen is mightier than the sword only because the pen can create ideas that inspire and guide a lot of swords.

Ideas without physical actions don't cause any effect. Ideas only outweigh actions to the extent that they result in larger actions.

If you start with any historically impactful idea and carefully trace its impact, you will see quite a lot of mass and energy moving around along the way.

And what is a sword without an idea? It lies there, inert, no threat to anyone. So when people talk about "the pen vs. the sword," what they're really talking about is a competition of ideas. Behind every sword there is thought--and pens can help change thought.

But none of this means that thought and ideas are non-physical. The relative impact of competing ideas might be non-linear and unpredictable, but physical systems can be non-linear and unpredictable.

The thing that consciousness has that is not simply an idea is sensation. At a certain point, it becomes indescribable.