Which principle does Pirsig refer when says "There's a principle in physics that if a thing can't be distinguished from anything else it doesn't exist"?

Why not the Pirsig principle?

Not certain whether this is physics or metaphysics.
Plato believed that things are what they are because of their forms. That is, we know the form and not the thing itself. We know the group or category a thing fits into, participates in, is made real by, and not the concrete particular thing.

From Luke Morris:

1. Everything that exists, exists in relation to something (or everything) else.

2. The identification (and quantification) of particular relationships is measurement.

3. Every existent bears some such relation or relations that can be measured (from 1 and 2). The measurable relationships exist even if the particular methods and standards of measurement in given cases have not yet been discovered, and even if exacting precision in measurement cannot be achieved. (This applies to relational concepts such as love, as well as to perceptually given concretes.)

4. Therefore, to be actually ‘immeasurable’ would be to bear no relation to anything else (from 3).

5. A thing that bears no relation to anything does not exist (from 1).

6. Therefore, an immeasurable thing cannot exist (from 4 and 5).

I wonder how this applies to the electrons of an atom. I don’t think there is any way of distinguishing one of an atom’s electrons from another.

Here is a counter-example from mathematics. If we assume that, at least in some abstract sense, complex numbers exist, there is no way of distinguishing i from -i. For any equation with i and -i terms, you can swap the i and -i terms and still have equality.

LostInParadise: Maybe it is rather understandable about electrons which are known by their spins, momenta and other quantum numbers. But in mathematics and generally in physics for example when we have lots of bosons in a quantum statistical mechanics scene, I don’t know how it works.

I think that it’s a far more basic principle of “science itself” or in an even larger sense “basic observation”.

If the thing being discussed can’t be distinguished from general background then the thing is a figment of the speaker’s imagination. (That is, speaking about “real things” in the physical world, because obviously emotions, promises, ideas and other metaphysical concepts are not “real” in an observable sense.)

@CWOTUS Emotions, ideas etc. can be observed by introspection.

To the OP: to my knowledge there is no such principle in physics.

Nice try, @olivier5, but my statement stands. I’m not claiming that metaphysical concepts such as emotions and ideas don’t exist, but they only exist in a subjective realm. You can only interact and “view” your own.

Certainly emotions and ideas exist, but they cannot be directly observed in a physical sense, and compared against other objects (or even, objectively, against other emotions and ideas). They can certainly manifest as a participant’s action or inaction, but they can’t be seen.

@CWOTUS What is “to see”, “to observe”, if not to watch a mental image constructed by the brain based on nervous stimuli? What is science, if not a set of ideas, or mental representations?

There’s such a thing as “mental objects”. In fact, that’s the only kind of objects we can know.

Olivier5: The author in the next sentences affirmed that there is something real other than object-subject and it is Value. He believed that subject-object metaphysics should be replaced by a metaphysics based on Value. Here is the next two sentence:
“To this the Metaphysics of Quality adds a second principle: if a thing has no value it isn’t distinguished from anything else.Then, putting the two together, a thing that has no value does not exist.”

I’ve no interest in metaphysics. It’s too lose a domain, close to theology. I am more interested in epistemology, the combination of observation and logic.

It seems obvious to me that ideas do exist. Otherwise one faces a logical paradox: the very assumption that ideas don’t exist IS ITSELF AN IDEA, a self-contradicting idea, and thus it cannot be true…

Values also exist, of course. There are a type of ideas.

I never really understood the difference between objects and subjects, by the way.

@olivier5 I believe that the discussion is about “things existing” in the physical sense, hence “in physics”. A physicist stating that idea would certainly be bright enough to understand that thoughts and ideas are subjectively real … but they are not objectively real in any way that can be measured or quantified in various ways (counting, for one thing, or weighed or dimensioned and compared to the non-existent metrics of any other idea), so in the sense of physics, “not real”.

Yes, ideas exist on a different level than physical things. They have no extension, no weight, no length. But they have their own metrics of sorts: for instance, that of “true or false”, that of “if… then” (logics). One can also measure their diffusion in society, e.g. through a poll or a referendum. One can trace their origins and evolution through space and time (eg “where/when does the concept of zero come from?”) so they are not completely etheral, unstructured or impossible to grasp.

Ideas also underwrite the measurement of physical objects. An observation is an idea. The metric system, or whatever system of weights and measures one uses, are sets of ideas. Etc.

To me, “real” means “whatever exists”. So ideas are real in that sense because they exist. Physical objects are only one part of reality.

Do ideas exist prior to being thought of?

@LostInParadise Sure, I don’t know if you do crossword puzzles but I have found that I can begin one in the morning, get frustrated and put it aside and then in the evening I can breeze through it, even the ones that gave me pause in the morning.

Now, why is that? Because the answers are there, my mind just has to find them.

Where do I find them? I pull them out of….the air! They are just floating around waiting to be discovered!

Now, where do they come from? Where were they in the morning? I don’t exactly know, they are just there when I look in the evening.

But I have a theory that actually, the answers are there because others have thought of them throughout the day and their thoughts have caused the answers to come into existence.

The problem with this is that it only explains why I can find them later in the day, not where the others who put them there found them in the first place.

Perhaps I have provided my share of answers in the morning and others have found the ones that I gave, but again this does not explain where I got them from in the first place but they have to exist in order to be discovered.

@rojo What you are describing looks very much like what Poincaré spoke of about intuition in mathematics. According to him, ideas are born out of an unconscious work of inventing and testing a large number of hypotheses, a work one does unconsciously while sleeping or doing the dishes or whatever. Like babies don’t pop up out of nowhere when they are born, but existed before that as embryos and foetuses.

There is a running debate in mathematical philosophy as to whether mathematics is discovered or invented.

I am on the discovery side, but this would be a good example of what the OP is asking about. How do you distinguish discovered math from invented math? There is of course no way to distinguish, so the distinction does not in fact exist.

All the talk about ideas – interesting as it is – has spun away from the OP’s original question about the question as it applies to physics. Since I was the one who originally brought up “ideas” as a stand-in for “things that do not exist in the physical world”, I take responsibility for the start of the thread drift. Sorry about that.

But the point is, getting back to physics and things that can be seen and touched or otherwise physically sensed, if there’s a particular significance attached to some object, but it’s a significance that can’t be discerned from other, similar objects, then a physicist is going to say that it’s a subjective significance only, and that “it doesn’t exist” for practical, real-world “physical” purposes.

For example, I have a pocket knife that holds a particular significance for me, because it came from my father. Aside from that personal significance, however, the knife is indistinguishable from others of its manufacturing run. (Let’s assume, that is, that all of the knives of that run were manufactured with perfect uniformity and have not met with various accidents and incidents that added “marks of significance” to them.) Then the personal-to-me significance of my father’s ownership, in the physical “real” world, does not exist, according to the physicist. And he’s right – in that sense.

A similar thing can be said about string theory and various other contenders for theory of everything. So far there has not been experimental evidence that can distinguish one from another, meaning that as of now no theory of everything exists.

@CWOTUS Except that there are no perfectly identical knives in the real world. It’s just a theoretical knife you’re talking about, not a real, physical one. You’re still talking of an idea here. And the same applies to any and all objects. There are all different, unique.

And even if there were two identical objects they would still be different by virtue of not being in the same place at the same time.

@LostInParadise It does seem like a discovery when you work through a proof, but to me it would be impossible. Ideas do not exist until they are thought of.

How did the planets in the Solar System manage to satisfy Newton’s laws, in their mathematical form, before Newton was born, if the laws did not exist until Newton thought of them?

Planets actually don’t satisfy Newton laws. That’s one of the reasons why general relativity replaced Newton’s theory of gravity. The apsidal precession of Mercury is the best known example.

Okay then, how did the planets follow the laws of relativity before Einstein?

They probably don’t either.