Maverick Philosopher

Nihil philosophicum a me alienum puto

To promote independent thought about ultimates. Philosophy, commentary on the passing scene, and whatever else turns my crank. Since 4 May 2004. By William F. Vallicella, Ph.D., Gold Canyon, Arizona, USA. Motto: "Study everything, join nothing." (Paul Brunton) Latin Motto: Omnia mea mecum porto. Turkish motto: Yol bilen kervana katilmaz. (He who knows the road does not join the caravan.) All material copyrighted.

Platonism Contra Physicalism in the Philosophy of Mathematics

It is a huge topic, but it is time to begin blogging my way into it as part of my protracted campaign against physicalism/materialism/naturalism in all its forms and wherever it may hide.

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Related Posts (on one page):

  1. Platonism Contra Physicalism in the Philosophy of Mathematics
  2. Some Bad Philosophy of Mathematics Exposed
Posted by William F. Vallicella on Thursday November 10, 2005 at 12:24pm
Malcolm Pollack (mail) (www):
Well, you know, set theory has some problems of its own.

As you point out, the number of possible sets is infinite. And as you say, the members of sets can themselves be sets.

What, then, about the set of all sets that do not contain themselves as members? What is the ontological status of that teratological entity?
11.10.2005 12:40pm
Malcolm Pollack (mail) (www):
Anyway, I might be missing something here, but how is your argument different from saying "we can imagine things that aren't physically real"? I look at a pile of things, and then I invent a concept, "set", and I make up some rules about what a "set" is going to be, and how a "set" is made up, and all of that. So now I have a nifty new thought in my mind about how things can be grouped together.

How does that thought now qualify as an "object"? Who's in charge of that?

Finally, did you know that the word "set" is the word that has the longest entry in most dictionaries?
11.10.2005 12:52pm
Celinda Stickles (mail) (www):
Bill,

(i) necessarily existent(existent in all metaphysically possible worlds)


What a about a world that was a true monad. Indivisible. Would these objects exist?

Also, it seems to me that these objects are mental in the sense that they are a result of they way we perceive the world. The only reason we conceive of numbers-degree of difference or enumeration- is because we perceive the world as a multiplicity and need some way to account for the realtionships between things. Admittedly once differences are postulated every possible world with differences has to include some self-consistent system of enumeration that will follow the same universal set of given rules, but it doesn't seem to me like this system is either necessary or outside our own mental processes.
11.10.2005 1:12pm
Malcolm Pollack (mail) (www):
I wrote above:
How does that thought now qualify as an "object"? Who's in charge of that?
Just to avoid confusion: while are-thoughts-really-objects? is an interesting topic all by itself, what is being claimed, I think, for sets is that they are independently existing abstract objects.

The point of my comment was to defend the view that they are actually only thoughts that we have.
11.10.2005 1:29pm
Bob Koepp (mail):
It seems that even if they have their causal origins in our perceptions of the physical world, mathematical objects are abstract in a way that perceptual objects are not. While we can, with more or less ease, conceive of possible worlds where the properties of various perceptual objects are very different from what we find in our actual world, mathematical objects seem to retain their properties across possible worlds. So even if mathematical objects are in some sense physical objects, it can't be in the "same way" that perceptual objects are. Can anybody provide even the rough outlines of a physicalistic account of the relevant difference?
11.10.2005 7:05pm
Rafael Caetano:

What, then, about the set of all sets that do not contain themselves as members? What is the ontological status of that teratological entity?


That problem was solved long ago. For that you must look into axiomatic set theory. In short, under appropriate axioms you cannot define such a set.
In any case, I don't think that's really germane to the post.
11.11.2005 6:07am
Malcolm Pollack (mail) (www):
No, Rafael, you're missing my point, which was germane "with bells on", as they say in England. Bill's post is claiming the independent, objective existence of a certain type of object, the "set". I am well aware that Russell's paradox was "solved" by an act of redefinition; that was exactly why I brought it up. My point is that the facts about what sort of objects can have objective existence shouldn't be a matter of human definition. Before Russell pointed out the problem, all were happy to think of the ordinary concept of a "set" as having an independent ontological reality, then, lo and behold, we find that doesn't work, and we have to declare a new concept, with a arbitrary, inelegant and watered-down definition. Hilbert and the rest of the mathematical community were aghast. The "set", which had seemed to be such a simple, natural entity, suddenly looked like a piece of Federal highway legislation. What will it be next week? Does the ontological status of these items change as we rewrite the math textbooks? Or is it more like: "No, we'll get it figured out. We thought that we had the inventory of mind-independent objects all worked out, but we're really almost there now."

Who are we kidding?
11.11.2005 8:08am
Celinda Stickles (mail) (www):
Bob, Thanks you put into words exactly what has been bothering me for a while, except that I am not saying mathematical objects are perceptual objects. When perceiving, what I perceive is a change in the properties of an object. However, within my mind I conceive of these changes as mathematical objects. Concepts are static, there are no verbs in logic because all concepts are objects, ie. nouns. I am not sure why this is so, and maybe you can come up with an example to show it isn't, I keep trying to think of one.

Anyway, since the conceptual world is static we cannot simultaneously conceive of the properties of objects and the relationship between those properties. Maybe you have noticed that mathematics is totally propertyless, it works only within an assumed homogenous substance. It only deals in differences, not properties. The efficacy of physics comes from the fact that although we conceive of the relationships and the properties separately, we can combine them when we take them back out of the mental world apply them to what we have perceived in the physical world.

To come up with some physicalistic account of this it seems to me we have to go back to neuroscience.

I think the reason that properties can be changed around so easily is that they are stored in a separate part of our brain then our perceptions, as individual pieces of information that we have the ability to "play" with when combining them. This is just a supposition from observing my own way of thinking and doing some research on learning. I have never read anything on how mathematicial information might be stored but if it is stored in a completely separate part of the brain from the properties this might account for the reason why these are so different.
What really gets me with all this is how our brain can be set up to figure out all the rules by which mathematics works. The rules themselves are completley determinate. While we can choose our symbols we cannot choose how to relate the symbols. It's like in one part of the brain the realtionships are chooseable and in the other the objects are chooseable.
11.11.2005 8:31am
Celinda Stickles (mail) (www):
Sorry that last sentence was poor let me try again. In mathematics we choose our signifiers but not how they relate. With properties these are the signifiers so we can choose how to relate them. I am still not sure this is real clear but I have to go get lunch for the kids.
11.11.2005 8:38am
Celinda Stickles (mail) (www):
Bill, sorry about the illogic in your comments. The last try still was a mess. For perceptual objects, what we seem to store are properties with no relationship between them at the basic level. Shape seems to be come from the mind drawing boundaries. (They have done studies that show that what we see when viewing something is the boundary between different qualia and that the brain then fills in this boundary with the color/texture qualia)So the process of assembling conceptual objects from basic percepts allows for an infinite variation in how we assemble conceptual objects.

In mathmatics what we seem to have is an ability to compare. So in mathematics we seem to have infinite ways to express relationships.
11.11.2005 9:49am
Bob Koepp (mail):
Hi Celinda -
I didn't think you were claiming that mathematical objects are perceptual objects, at least not in the "same way" (that Wittgensteinian problematic, again) that physical objects are perceptual, or perhaps constructed by idealization from perceptual objects (this thing called 'idealization' is another hornets' nest).

However, I don't think that perception is always and only of changing properties -- else there would be no problem of perceptual constancy. And logic/mathematics is not all nouns -- we need operators as well as operands.

The problem I was trying to highlight is that however nicely we can effect mappings between the physical world and mathematics, that such mapping is possible doesn't help us to understand how it is that mathematical objects seem to possess their properties in ways very different from the way physical objects possess their properties. It should be one of the first orders of business for those who claim mathematical objects are physical to explain (or explain away) the seeming difference.
11.11.2005 9:50am
Steve Esser (mail) (www):
I don't know if this will be helpful, but here's how I understand the argument (as a non-expert): By virtue of WHAT are mathematical statements true? If they are true by virtue of reference to physical objects we perceive, we cannot account for mathematics involving infinities. If they are true only because I think them up as concepts in my mind, then how can I refute someone who asserts that "4 is prime" is true in their mind?

Finally, mathematicians mostly insist they "discover" new maths, they don't invent them. They are mind-independent and (more arguably to me) physical object-independent.
11.11.2005 10:14am
Malcolm Pollack (mail) (www):
Hi Steve,

What mathematicians insist about their discoveries isn't necessarily the final word on the subject, I'd say. They might simply be wrong. Also, you say they "mostly" insist; what then is the source of their disagreement, and how do we know who is right?

Bob, I agree that mathematical objects don't possess their properties in the same way physical objects do. What I was suggesting is the possibility that mathematical objects are thoughts that we have. I am certainly not claiming that mathematical objects are physical objects, any more than the rest of our thoughts are. The physicalist interpretation, I suppose, would be that our thoughts are states of our neuroanatomy.
11.11.2005 11:58am
Malcolm Pollack (mail) (www):
Hi again Steve,

Posted too soon. (There's probably some sort of ointment that prevents that.)

To refute someone who claims that 4 is prime, I'd ask him simply to explain his thinking on the matter - what he means by "4", by "prime" and what his idea of mathematics is generally.

Keep in mind that non-Euclidean geometry, the calculus of infinitesimals, and transfinite and imaginary numbers used to seem as plainly wrong as "4 is prime."
11.11.2005 12:03pm
Steve Esser (mail) (www):
Hi Malcolm. My too-sweeping claim about what mathematicians think is based on a memory (which is fallible) of seeing a survey of mathematicians where platonism was pitted against formalism and came out ahead. I will look to see if I can find the reference. Formalism I take to be the position that the symbol manipulation should not be thought of representing anything real ("shut up and calculate").

On the second point, I was thinking that the ability to convince everyone that there is a correct view of a mathematical proposition points to its objective status. As for non-Euclidean geometry, calculus et.al: were they thought of as wrong or just not discovered yet? Was there a long-lasting community of dissenters to these ideas?
11.11.2005 12:37pm
Malcolm Pollack (mail) (www):
Oh yes. George Berkeley, for example, famously scoffed at the infinitesimals used in calculus, calling them "the ghosts of departed quantities." It wasn't until calculus had proved itself over many years to be an amazingly useful practical tool that skeptics just decided to give up the fight.

The problem with using your being able to convince everybody of the correctness of a mathematical proposition as proof of its ontological mind-independence is that everyone around you (in these parts, at least) has, basically, the same kind of mind. In the same way, I would have no trouble establishing here in New York City the ontological certainty of the proposition "George Bush is an idiot."
11.11.2005 1:38pm
Dave Gudeman (www):
Two formal points:

Celinda, in a world that contained only one object, there would still be an infinite number of sets. In fact, in a world of no objects there are an infinite number of sets. Obviously there is the empty set, {}, there is also the set ONE containing the empty set, {{}}. There is also the set TWO containing the empty set and ONE, {{},{{}}}, etc.

Malcolm, George Berkeley's criticisms of calculus were specifically about Newton's calculus, and Berkeley's criticisms were valid. Newton's formulation of the calculus was sloppy and did not hold up to inspection. No amount of "proving itself" would ever have made Newton's calculus acceptable to rigorous mathematicians.

Eventually Newton's calculus was thrown out and replaced by the theory of limits, which was not vulnerable to Berkeley's criticisms.
11.11.2005 2:36pm
Bill Vallicella (mail) (www):
Steve Esser wrote above:


...here's how I understand the argument (as a non-expert): By virtue of WHAT are mathematical statements true? If they are true by virtue of reference to physical objects we perceive, we cannot account for mathematics involving infinities. If they are true only because I think them up as concepts in my mind, then how can I refute someone who asserts that "4 is prime" is true in their mind?


That's right. We all agree that statements like '7 is prime' are true. What makes them true? What must the world be like for them to be true? Must there be something outside the mind and language for them to be about? If yes, could those things be physical? The point of my little argument was that, if there must be something extramental to serve as truth-makers for math truths, then those truth-makers cannot be physical: math objects far, far outrun physical objects.

If there is even one set, then there is an infinity of sets.
11.11.2005 3:12pm
Bill Vallicella (mail) (www):
Dave:

Good response to Celinda. But if 'object' is used to cover absolutely everything, then it covers sets as well. It follows that in a world with no objects, there would be no sets, not even the empty or null set. One might take this to show that there cannot be a possible world in which there is nothing at all.

Perhaps you are using 'object' to cover non-sets.
11.11.2005 3:22pm
Bill Vallicella (mail) (www):
Malcolm;

Your suggestion seems to be that there is no mathematical reality. But I take it you think there is a physical reality. Is that what you are saying?
11.11.2005 3:37pm
Bill Vallicella (mail) (www):
Malcolm,

You are missing the point of the argument inasmuch as I was assuming that there is something external to the mind that math statements are about, and then arguing that they cannot be physical objects. You are questioning that assumption. But I dealt with that in an earlier post. In other words, there are two distinct questions:

Q1. Do math statements correspond to anything extralinguistic/extramental?

Q2. If yes to Q1, then: are those extramental things physical or Platonic or something else?

I was dealing with Q2 in the present post.
11.11.2005 3:47pm
Dave Gudeman (www):
Bill, I was using "object" to refer to physical objects.
11.11.2005 7:29pm
Robert (mail) (www):
Bill,

My answer to Q1. is no, because numbers, sets and all of mathematics are symbols and the manipulation thereof according to certain rule sets. Some of mathematics manipulates symbols according to rules that produce useful results--a bridge that stands for centuries. Some math has no necessary relation to the physical universe--the properties of infinities, perhaps.

Imagine a universe identical to ours but with no human beings. Where are the 'prime numbers,' the 'number 4' and 'sets?' In such a universe there are only physical objects. We created these concepts and without us they have no meaning.

Therefore numbers cannot be identified with physical objects whence it follows that not everything is a physical object!


I agree heartily with all of the statements in the post up to the very last six words, the truth of which depends on the definition of (every)'thing.' Here is the heart of the question.

In some sense the univserse is just a soup of myriad whirling particles, which are simply denser in some places than others. Our minds abstract objects and create boundries out of this stuff. These boundaries define physical 'things.' I would argue minds also create the relationships that are concepts. If a relationship is a 'thing' then not everything is a physical object. That's the crux, in my understanding.
11.11.2005 11:22pm
Bill Vallicella (mail) (www):
Malcolm et al.

Chess tournament today and tomorrow. But I hope to respond to (some) of these very good comments. Thanks and enjoy your weekend.
11.12.2005 5:02am
Henry Verheggen:
Malcolm, you said,

“numbers, sets and all of mathematics are symbols and the manipulation thereof according to certain rule sets.”

IIRC, Gödel’s incompleteness or undecidability theorems were designed precisely to disprove this.
11.12.2005 5:48am
Henry Verheggen:
Malcolm, you also said,

"Our minds abstract objects and create boundries out of this stuff."

If this is so, wouldn’t it also be true that not only are relationships not physical things, but there are no physical things. If there are no physical things, if things are merely conventional, then that is a problem for physicalism, I would think. Especially so for fundamental physical entities that are held to exist by virtue of mathematical models such as the infinite dimensional Hilbert space where quantum mechanics lives.
11.12.2005 7:23am
Malcolm Pollack (mail) (www):
Hi Henry,

Just back from a tiring college-visiting excursion...

I didn't say either of those things! That was Robert.

Too tired to comment at the moment.
11.12.2005 6:57pm
Malcolm Pollack (mail) (www):
Good luck in Caissa's arena, Bill!
11.12.2005 6:58pm
Henry Verheggen:
Yikes! Sorry Malcolm.
11.12.2005 7:11pm
Dave Gudeman (www):
Robert, if mathematics is just the manipulation of symbols, how do we know that it applies to anything besides the symbols? For example, I count out 10 party guests and because I want two sodas for each guest, I write down the symbols 2*10=x. I follow the rules of this arbitrary symbolic game that you claim mathematics is and get x=20.

If this is nothing but an arbitrary game of symbol manipulation, then why should I have any confidence that I can go to the story, buy 20 cans of soda then have two sodas for each guest?

It can't be an arbitrary game. The rules of the game must be the correct rules. They have to be the rules that will give the correct answers. The question is, how do we know what the correct rules are? I say that the correct rules are the rules that always produce true statements about numbers from true statements about numbers.

If there are no numbers, then there are no true statements about numbers.
11.13.2005 1:03pm
Robert (mail) (www):
I'm going to write a longer post to expand on my ideas on this topic. What an excellent set of comments and commenters (myself not necessarily included!).

Briefly for now: Henry, there certainly are physical things. My argument is that we essentially create the boundaries between them and then give what we consider to be entities a name, after which they have a separateness to them that's only in the eye of the beholder. Example, a 'cloud' in the sky. It may seem to have sharply defined boundaries from the ground, but it doesn't.

But upon further consideration I think that I was wrong on Bills' Q1., even if my points were good...more later; must go.
11.13.2005 10:35pm
Henry Verheggen:
Robert, I don't disagree with you on the point about boundaries. The problem is spelled out in "The Problem of the Many" in the Stanford Encyclopedia. Peter Unger concluded from this problem that there are no things. I am not sure he still believes this, but he still uses the problem of the many in his critique of physicalism.

To expand a bit on one thing I said: the existence of some physical entities is inferred only through a mathematical formalism. One of these is the quantum wave function. The space in which the formalism works is not only infinite dimensional in some cases, but is complex in the sense of the ordered pair (a, ib). We can't seem to form any clear idea of what this entity is in a physical sense other than through an abstract formalism.
11.14.2005 5:54am
Henry Verheggen:
A brief reply to Malcolm's argument about Russell's paradox (RP): If RP casts doubt on the foundations of mathematics, I'm not sure it helps Malcolm's position either. If RP shows that the notion of a set is just a product of our conceptual apparatus, a human convention subject to revision, it also shows that there is something wrong with our conceptual apparatus at the level of fundamental intuitions. If something so basic can go wrong in our minds, then how can we rely on it for anything more complex or intuitively difficult? On the other hand if we want to find out where our intuitions go wrong, we will have to assume that we have the capacity to transcend our failures and discern the objective truth.

PS. A paper relevant to this topic is:

On the Necessary Existence of Numbers
Neil Tennant
available online
11.14.2005 11:07am
Bob Koepp (mail):
Just a word of caution about assuming that _boundaries_ define physical things. There's an alternative view that what might be called _central tendencies_ play this role, in at least some cases (e.g., color categories). Where this alternative paradigm is appropriate, the lack of sharply defined boundaries isn't obviously problematic.
11.14.2005 11:52am
Celinda Stickles (mail) (www):

Bill,

What if the universal, unchangeable nature of mathematics is caused by the way we are made ie. the "hard wiring" in our brain? Would this constitute be an abstract object under your definition or would they be wholly mental objects?
11.14.2005 12:26pm
Robert (mail) (www):
My apologies to Bill and our other commenters for not having read his previous post (and the many comments thereto) before commenting on this one.

But having spent most of my lunch time on that one I now have more food for thought than I can easily digest quickly...But in regard to the current post, I believe I have an example that might support the last sentence, the truth of which I stated hung on a definition of 'thing.'


Therefore numbers cannot be identified with physical objects whence it follows that not everything is a physical object!

Concepts (including mathematics) can effect physical change in the world; therefore, they are 'things.'

A good example are those drawings designed to fool the eye--one looks and sees a 'young lady,' then someone simply says the words 'old lady' and you see the picture entirely differently! A concept has affected a physical change in the brain, as far as I can tell. It wasn't the mere vibrations of air in your eardrums that caused the new perception, it was an idea.

The use of mathematical concepts like 'number' and 'set' seem to operate in a similar fashion, as non-physical objects.
11.14.2005 12:34pm
Dave Gudeman (www):
Robert, you make a good point. When someone says that numbers and other abstractions have no causal power, there is an implicit qualification: except through the medium of the mind. Clearly, a number can cause people to behave differently: you put in four cups of flour because the recipe presents you with the concept of four.

However, it isn't at all obvious that this happens because the concept does (or even possibly can) cause a physical change in the brain (except, again, mediated by the mind). You should look through Bill's archives of the last couple of months for some more food for thought).

What suddenly occurs to me is that this observation pretty much prevents a mind/body physicalist from being a realist with respect to abstract objects. If he were, he would have to explain how abstractions can have direct physical influence on the brain.

Bill: has anyone ever addressed this point?
11.16.2005 12:39am
Malcolm Pollack (mail) (www):
Well, right you are, Dave - I for one do indeed have difficulty being a realist with regard to abstract objects.

I've been "offline" for a few days and missed some interesting discussion here.

As for Robert's comment just above, the physicalist response would be that it in fact WAS the vibrations of air in the eardrums. They pushed the brain into a different state, and that new state in turn caused relevant output. "Idea" is just a high-level description of this underlying process.

Perceiving an ambiguous optical illusion one way or another merely means that the same input is capable of driving the brain into two or more states. Which one is chosen presumably depends on inner or outer context.
11.18.2005 12:47pm
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