Decidability and Truth
In "What is Metaphysics? Yet Again," we were discussing whether metaphysical statements have truth value, i.e. whether or not they can be true or false. RG Collingwood, @tim wood, and I say no. @Janus was unconvinced. Quite a few times, I've said that if we can't determine if a statement is true or false, even in principle, then it is either metaphysical or meaningless. Then Janus came up with this, which set me thinking:
Quoting Janus
So that's the question. Two questions. 1) Can a statement be true or false if it is not possible to determine which it is, even in principle? Then, if we can decide that question, 2) What happens if we can't determine if the truth of a statement is decidable in principle or not?
The subject where this issue most often comes to mind for me is interpretations of quantum mechanics and, in particular, the multiverse interpretation. In my mind, unless there is an experiment or theoretical development that can determine which interpretation is correct, then anything beyond the Shut Up and Calculate Interpretation is meaningless.
Although the subject may come up, this is not a discussion about what metaphysics is or is not. That's what my previous thread was about. It is also not a discussion of which interpretation of QM is correct. I'd like to keep this thread focused on the specific questions I asked. I'm curious to see if that's possible.
Quoting Janus
I can't decide whether the question as to whether propositions that are undecidable for us can nonetheless be true or false is itself undecidable or not,
So that's the question. Two questions. 1) Can a statement be true or false if it is not possible to determine which it is, even in principle? Then, if we can decide that question, 2) What happens if we can't determine if the truth of a statement is decidable in principle or not?
The subject where this issue most often comes to mind for me is interpretations of quantum mechanics and, in particular, the multiverse interpretation. In my mind, unless there is an experiment or theoretical development that can determine which interpretation is correct, then anything beyond the Shut Up and Calculate Interpretation is meaningless.
Although the subject may come up, this is not a discussion about what metaphysics is or is not. That's what my previous thread was about. It is also not a discussion of which interpretation of QM is correct. I'd like to keep this thread focused on the specific questions I asked. I'm curious to see if that's possible.
Comments (143)
Can such a statement be constructed?
"This statement is true or it is not possible to determine that this statement is true".
If the statement is false, then it is not possible to determine that it is true. It can't be determined to be true if it is false.
If the statement is true, nothing is said about it's being determinate - the left of the disjunction can have either value.
So the truth value of the statement cannot be determined.
I started working on a response to your post but quickly started running around in circles. I'm still thinking about it and I'll get back to you later.
I want to clarify this. Do you mean we have an idea that we can conceivably prove to be true or false, but we don't currently have the means to do it? Or do you mean an idea that we have no conceivable means of even trying to prove it true or false?
So for example, someone might say, "Tomorrow I may die." In this case, you have to wait until tomorrow to come for you to figure out if you do indeed die tomorrow.
However, if I say, "Tomorrow I will die in my sleep.", will you ever be able to confirm that? I'm assuming of course that in your sleep you would not be conscious of your death. So if you died, you would never know. But lets say you don't die tomorrow, but go into a deep coma. You then die the following day. In this case, it was impossible for you to confirm whether your statement was true or false.
The example I used in the OP may clarify things.
I think the multiverse interpretation of quantum mechanics is meaningless because I believe it is not possible to demonstrate if it is true or false, but, I can't prove it is not possible. Given that, what is the status of the multiverse interpretation.
Ok, I think I see what you're going for. In this case, I would say you would know what it would take to prove multiverse theory true or false, (humanity discovering an answer), you just believe it is impossible that humanity will ever have the capability to do so.
This is really a combined question with a premise.
a. It is impossible for humanity to ever discover if multiverse theory is true or false.
b. Consequently, the multiverse interpretation of quantum mechanics is meaningless.
As some could quibble with "meaningless", lets change it to "unprovable".
If A is true, then b is true by consequence. But it could happen that tomorrow mankind discovers multiverse theory is true or false. Therefore this proposal is more of a prediction such as, "Tomorrow the sun will rise again." As such, the only thing we can do in this case is wait. Maybe humanity will discover the truth about multiverse theory, and maybe they won't.
Yes, I think you've laid the argument out correctly. You've raised another question in my mind. Here it is:
Since there is no evidence whether it is possible to determine the truth or falseness of the multiverse interpretation of QM, should that interpretation be given serious consideration as a scientific theory?
In short, no. But that theory might inspire funding into trying to see if its possible to prove multiverse theory. You would absolutely need to prove multiverse theory first. But humans are often times fueled by dreams that lead us to truths we would never find otherwise.
Me too.
"This statement is true and it is not possible to determine that this statement is true" seems to be determinately false.
"This statement is true or it is not possible to determine that this statement is false"... well, if it is true, then of course one can't determine it to be false, so that looks determinately true.
Then we could play with conditionals...
"If it is not possible to determine that this statement is true then it is true"...
There may be no evidence today determining the truth or falseness of the multiverse interpretation of QM, but there may be evidence next year. As @Philosophim wrote: "Maybe humanity will discover the truth about multiverse theory, and maybe they won't"
Question 1) refers to a proposition that it is not possible even in principle to determine whether true or false.
As it may be possible to determine whether the proposition "there is a multiverse" is true or false, it is therefore possible in principle to determine that the proposition "there is a multiverse" is true or false.
Therefore, question 1) has no bearing on statement 1).
(Although I am not sure everyone would agree that there is no evidence for a multiverse)
This doesn't seem to lead anywhere, because it involves a vicious epistemic circle. Truth or falsity are established in the framework of some epistemic standards. Janus's statement questions one epistemic standard, which is fine, but the resolution will require some other epistemic standards, distinct from the one that is being questioned.
Let's, arguendo, agree that you're right and metaphysical claims, for reasons we need to be informed of, can't be true/false.
The following are neither true nor false:
1. Cook
2 Kplx zgfd
3. This sentence is false (liar sentence)
4. &×*
.
.
.
Then, as per you, the following too are neither true nor false:
1. Free will exists
2. God doesn't exist
.
.
.
Are you saying "Kplx zgfd" = "God doesn't exist"? Am I missing something?
Starting with @T Clark's question "Can a statement be true or false if it is not possible to determine which it is, even in principle?"
Considering "there is a god beyond our comprehension" as an example of a proposition which we can never know even in principle whether true or false.
So, the answer to @T Clark's question is yes, a proposition such as "there is a god beyond our comprehension" not only can be true or false but must be either true or false.
In answer to @SophistiCat's question as to where does this lead, it leads to the knowledge that there are some things that are beyond our comprehension.
That's the question I'm wrestling with. I think, although I'm not sure, that there's a standard that has to be met. It's like they say, you can't prove a negative. There has to be a point where I stop and say "We've found no evidence. We can't see any way of testing this hypothesis. That's the best we can do." I don't know if we are at that place yet with the QM multiverse interpretation or, say, string theory. It is my understanding that many scientists think we are.
An example would be helpful if you can think of one.
1, 2, and 4 are not propositions. This argument doesn't apply to them. 3, the liar's paradox has always bothered me. @Banno made a similar comment earlier in the thread. I'm still working on a response.
Quoting TheMadFool
I think "Free will exists" is a metaphysical question and is neither true nor false. Let's not get into a discussion of the merits of that position right now. I've acknowledged several times in various threads that I am ambivalent about how existence of a specific God or gods fits into metaphysics. It would seem that the existence of the Christian God is a matter of fact, and, thus, not a metaphysical question. Again, I don't want to get into the specifics of this particular issue in this thread.
Quoting TheMadFool
I don't think your argument, to the extent your response even provides one, has any merit.
I don't understand how you reach that conclusion.
Quoting RussellA
I don't agree with that either.
Speaking of epistemic standards, or perhaps just clarifying the question: how do you judge whether a proposition is true or false, decidable or undecidable? Does truth or falsity just mean your opinion on the matter, or do you mean objective truth? By decidable do you mean whether you are able to make up your mind or, again, decidability in some objective sense?
Do you consider any method of evaluation or something more specific, e.g. empirical, scientific test? (When you talk about interpretations of quantum mechanics, for example, it sounds like you mean the latter, to the exclusion of any other standard.)
Any of these questions admit multiple answers, depending on what you want to do. The trick in not getting bogged down in pseudo-paradoxes is being upfront and consistent.
Justification
Quoting SophistiCat
That is the question on the table. Here's what I wrote in a previous response to @RussellA.
Quoting T Clark
Quoting SophistiCat
It is my understanding that all interpretations of QM are equivalent in that they have not been verified and may not be verifiable.
I call these philosophies Gandolfian theories. There are plenty of people who postulate what Gandolf from The Lord of the Rings would do in a certain situation. How was he feeling? How was he thinking? But at the end of the day, everyone forgot that Gandalf wasn't real. if he was real, we could take all of these conversations seriously, and it would probably solve a lot of problems and mysteries in life. But he's not.
For me, to find that part where I say, "There's no way of testing this hypothesis," I invent a hypothesis that cannot be tested, and try to think why I cannot test it. Take an invisible unicorn for example. Perhaps there are invisible undectable unicorns that exist. It seems in our head like it could be true. But that's nothing we can actively test in reality, because its undetectable.
If you cannot apply an idea to reality, then it is a Gandolfian idea. It can be a lot of fun to think about, but ultimately, its fiction.
Don't forget to include me in your reply after you've thought things through.
Quoting T Clark
1. Non-propositions are neither true nor false.
2. Metaphysical claims are neither true nor false.
How do you distinguish non-propositions from metaphysical claims?
Yep.
Aesthetics?
Quoting T Clark
Well, that doesn't say much. Justification for whom? Just you, or "us" (as in your response to RussellA), or some kind of objective justification (if that's not an oxymoron)? And what kind of justification?
If it is a matter of what you personally hold to be true or false, decided, undecided or undecidable, then there doesn't seem to be much to puzzle over. Whatever isn't decidedly true or false is perforce neither true nor false. So setting setting that edge case aside, what is it exactly that you are asking?
Quoting T Clark
Interpretations of QM are equivalent with respect to a particular epistemic standard: that of being empirically distinguishable. But some people prefer one interpretation to another, even while acknowledging that they are empirically indistinguishable. So clearly there can be other epistemic standards at work.
Depends on how truth is understood. Some will insist that there can be no use to asserting a proposition whose status is unknowable, so it's just a bad question.
A realist might be bound to say there is a use for this sort of thing.
Quoting T Clark
Methodological realism.
When it comes to metaphysics, a pulchra mendacium (beautiful lie) is acceptable and maybe even desirable/preferrable à la gennaion pseudos (noble lie)?
Imagine if people knew for certain God was a fairy tale?
Bedlam!
But a lie is false.
@T Clark's question is about statements the truth of which are indeterminate. A lie does not have an indeterminate truth value. It is false.
To be true or false as a particular claim requires meeting the test of being a statement to which both the principle of noncontradiction and the law of the excluded middle apply.
If the the PNC fails to apply, the statement is logically vague. It is neither true nor false.
If the LEM fails to apply, the statement is logically general. I would say this covers the recursive or self-referential case where the statement is seemingly both true and false at the same time.
Quoting T Clark
In practice, decidability is a pragmatic exercise. I would say that while we can model the world as if it has counterfactual definiteness all the way down - and so is seems that bivalent logic ought to apply - in fact Nature I only admits to being relatively divided. This makes it vague or indeterminate at base.
This is a view quantum theory looks to confirm. The Planck constant defines a fundamental grain of uncertainty.
So there are three ways to go on quantum decoherence. You can get hung up on the bivalent question of whether there is a definite collapse to classicality or instead no collapse and hence MWI. The third answer would be to say that decoherence is a reduction towards classicality, but never a complete one. Some degree of indeterminacy or vagueness remains. The PNC never completely applies.
So both MWI and classicality get ruled out as being logically imposed fictions on our metaphysics. If we expand our metaphysics to include the concepts of vagueness and generality, some of the major historical blocks on metaphysical thought start to fall away.
But we do know that Thor is a fairytale.
Indeed! However what's the best course of action when you don't know if a proposition is true or false? Assuming it's false seems more reasonable than assuming it's true.
Too, @T Clark hasn't really said anything about how metaphysical claims aren't true or false. They are clearly propositions as per the objections he raised to my post.
Another issue is whether he means to say metaphysical claims can be true/false but can't be verified/falsified like peusdoscience or does he think that metaphysical claims are propositions to which truth values are N/A?
In addition, what about other truth values like both true and false (neither true nor false is a contradiction) and what of multivalent logic? T Clark's stand on metaphysical claims is very Buddhist. See Nagarjuna's tetralemma and Siddhartha Gautama's cryptic response to the metaphysical question "does the Buddha live after death?" @Wayfarer will probably explain it better.
The notion that metaphysical statements are neither true nor false won't bare a load. Metaphysical statements are taken as true, but unjustified.
Like that the bishop stays on it's own coloured squares. There's no reason for it, but it is true.
You mean true/false, right?
Of course if this is some kind of Gödelian move, I'm willing to get on board.
No. I mean "true"
You can't play chess unless you take it as granted that the bishop moves on the one colour.
You can't shut the door unless you posit a door to be shut. Hence, realism.
But we are now off-topic.
So, the two metaphysical claims below are both true?
1. God exists
2. God doesn't exist
?
So, the two chess claims below are both true:
1. The bishop moves diagonally
2. The bishop moves orthogonally.
No.
So God exists. There is no God.
We must take these statements as both true, and both requiring their own justification, rather than being a single counterfactual in which the degree to which one can be shown false, the other becomes accepted as true?
Sounds legit.
Let's try this hypothesis:
On a rocky planet, moon, or asteroid somewhere in this universe we call home, located one kilometer beneath the surface, is a rock formed in the exact shape and size of a 1909 svdb US copper penny.
So, there are ~10^23 stars in the universe. Let's say there's one candidate location in each star system and we can check one location every second, including travel time. Given there have been about 4 x 10^17 seconds since the universe began, that means it would take more than 2 million times as long as the universe has been around to check all the locations. Somebody check my math. Obviously, this is a very, very, very^15, conservative estimate of how long it would actually take.
To me, our hypothesis is neither true nor false. It has no truth value. It is metaphysical or meaningless. I think that's my pragmatist voice speaking.
The Buddhist is concerned with a practical task, i.e. liberation from inner conflict etc. Metaphysical questions are regarded as a distraction. (Murti notes that such 'undetermined questions' have exact parallels with Kant's 'antinomies of reason' in Central Philosophy of Buddhism.)
I regard metaphysics as a worthwhile subject within a domain of discourse. The starting point of that domain of discourse are the themes in Aristotle's Metaphysics - understanding their historical precedents, how Aristotle expressed them, and how they developed in the subsequent centuries. That is a 'word game' that can be played out regardless of whether you believe any of the content or not. The thing is to try and understand the subject on its own terms. So I think the question in the OP is not on the right track, we're never going to be able to decide the truth or falsehood of classical metaphysics outside the criteria provided within that domain of discourse (especially if the Tao te Ching is taken as a metaphysical text, which it is not.)
I'm not interested in going into that. Perhaps someone else will.
So … not yes? :smile:
This is not intended to be a discussion about what constitutes justification. I would enjoy participating in one if you start it. So, I'll punt - by whatever standard of justification we can agree on.
Quoting SophistiCat
Yes, that's what I meant when I wrote that all interpretations are equivalent.
Quoting SophistiCat
In my judgement, interpretations that are empirically indistinguishable are the same thing. Differences between them are meaningless.
Yes, this is the issue I started this thread to discuss.
I've said more than enough about how metaphysical claims aren't true or false. Which isn't the same as saying I've convinced you or others.
Refer back to "What is metaphysics? Yet again." That thread has taken that question about as far as I am interested in taking it right now. This is a new question, a new thread.
Quoting TheMadFool
No, it's not.
Quoting TheMadFool
No, it's not.
Needless to say, I disagree.
Of course it is.
I agree, although I'm not sure I mean the same thing by that statement as you do.
Quoting apokrisis
Do you mean that as a scientific statement in relation to quantum indeterminism or a metaphysical statement about truth and falsity in general.
Quoting T Clark
At the least we need a way of distinguishing your mooted statements that are neither true nor false from other sentences that are mere nonsense - not even either true or false.
Otherwise the claim that metaphysics is nonsense rings hollow.
Why don't you and @TheMadFool take that on. It isn't really relevant to the issues I'm interested in this thread.
Quoting Banno
I never said that metaphysics is nonsense. Your just trying to be difficult.
Yep. Goes with the job.
Ok, I'll leave off that - seems the thread is headed off into pragmatics anyway. Let me know what you decide about the undecidable sentence in my first post.
I don't generally find the liar's paradox very helpful in sorting things out, but I'll take a shot.
Let's start with "This statement is true," and see where that gets us. My intuition tells me 1) It can be decided whether or not the statement has a truth value and 2) The statement has no truth value. I'm not sure I can justify either assertion.
The problem is caused by the sentence's self-reference. Let's try out a couple of self-referential sentences that do have truth values:
"This sentence has five words." - That's true.
“This sentence has seven words.” That’s false.
"This sentence has an unknown number of words." - That's false. I think.
Sorry, I’m not getting anywhere. I don’t think the liar’s paradox is central to my thoughts about the decidability of the truth value of propositions, but I’d like to figure it out. I’m putting it on my list for a separate thread sometime.
I just posted my response, which was basically just me giving up.
I’m saying that the term ‘metaphysics’ has a scope, defined originally against Aristotle, developed by the subsequent tradition. Tao Te Ching falls outside the scope. As does Vedanta and Buddhism. Which is not to say that those texts and traditions don’t deal with some of the same subjects, but they do so in very different terms, different languages and different cultural tropes. When you try and combine them all into some grand meta-subject called ‘metaphysics’ then you loose a great deal of specificity which is why you can’t find any criteria for deciding their truth or falsehood.
I don't think your understanding of the meaning of "metaphysics" is consistent with how the word is generally used in philosophical discussions. It certainly isn't consistent with how I use the word.
Its not quite the liar's paradox; more like a twisted Godel sentence that shows itself to be inherently urndecdeable.
Nor is self-reference the problem, since as you show there are quite reasonable, non-paradoxical self-referential sentences, and there are also paradoxes that do not rely on self-reference.
But moreover,
"This statement is true or it is not possible to determine that this statement is true".
isn't paradoxical, if a paradox is both true and false. The issue is not that the sentence is both true and false but that the sentence is undecidable.
SO the answer to your questions:
Quoting T Clark
Seems to me we can assign "true" or "false" to the above sentence without contradiction, so the answer is "yes, there can be sentences that are true or false but undecidable".
Alternately, we might adopt a triadic logic and assign it the value "indeterminate".
Very little. There are, after all, other things which we not only don't know, but can't know. But we muddle on.
We can't determine if Caesar stepped into the Rubicon with his left foot. But undoubtedly he either did or din't.
Both. Metaphysics is in general the application of reason or rationality to the understanding of nature. Logic, or logics, are its tool. Then physics is metaphysically derived intuitions, shaped up into formal mathematical exactness, and then subjected to the informality of acts of measurement. At some point, we just agree that the evidence is “good enough”.
The central issue in the OP is he question of “which logic” ought to guide our metaphysical intuitions?
This could be good old fashioned reductionism. But history has shown that dialectical and trialectic reasoning - a move towards holism - actually deliver the better results when it comes to the forming of general intuitions. Reductionist predicate logic is what you use more in the next step of forming deductive statements that are then suitable for a process of inductive confirmation, or the experimental test of a bivalently-framed prediction.
So one thing that is clear to any logical holist is that yes/no thinking lacks sufficient sophistication. You need further categories - a third option as an answer, such as yes, no, or vague.
Pragmatism builds that answer in. The theory makes some kind of reductively bivalent claim about reality. It is a good thing to be clear in this way. But then the theory is only ever deemed verified or falsified provisionally. The evidence might lean heavily on way or the other. But always, the fact is that there remains something ambiguous or indeterminate about its truth status.
Then when it comes to quantum theory, we find ourselves bumping up against the fact that nature itself must have this same kind of logical holism. The vagueness that we need to include in our epistemic methodology becomes also a useful third category when we speak of nature “in itself”.
The alternative is to form pathological metaphysical intuitions like claiming QM proves there is a multiverse, or forever protesting that there must be “hidden variables” still to uncover.
:lol:
Discuss as in determine who's right? Or just to understand the diverging narratives?
I don't think there's a right or wrong here. I'm just trying to get my head around the issue. It's something that comes up a lot in discussions.
The question in my mind was not about establishing truth or falsity, but as to whether we should think that there could be truths that can never, even in principle, be established. Of course, it is true that anything we could never establish could be of no import to us. But the question is not about whether something is of import to us, but whether truth is completely independent of our interests or our ability to establish it.
You're right about one thing, though; the question doesn't really lead anywhere, especially if you think, as I do that it is undecidable. The best it could offer would be by way of the most general orientation to things.
Wouldn’t that be more the domain of natural philosophy i.e. science? Like, for example, physics is observing experimental results. Metaphysics is considering what they mean (as in the interminable debates about quantum physics.)
Similar to the idea of 'naturalised epistemology' in analytical philosophy.
@T Clark had said that the question of God's existence is truth apt (unlike absolute presuppositions; a point I'm still not clear about). Someone else raised the mutliverse conjecture, and someone said we may answer be able to answer this. I don't think this is correct; the truth of even testable scientific theories can never be determined; all we know is they work...until they don't...or another theory works better.
So, now we have two examples of possibilities we can imagine the truth of which can never be determined, even in principle. It seems natural to think that despite our inability to determine the truth status of such imagined possibilities, that there must be some truth of the matter regarding them.
I think that the truth-status of such conjectures is undecidable; that is I can't decide whether we should say they could be true or false, or that they cannot be true or false.
If it is not possible to determine even in principle whether the proposition "a multiverse exists" is true/false, then the first problem is not whether the proposition "a multiverse exists" is true or false, but what does "multiverse" mean.
We have the concept multiverse, but if we can never know even in principle whether multiverses exist or not, our concept of multiverse must remain fictional, as a unicorn or Conan Doyle.
IE, if we can never determine even in principle whether the proposition "a multiverse exists" is true or false, then the "multiverse" must remain a fictional entity, as a unicorn or Conan Doyle.
Technically I would say "It may be true or false, but it is extremely likely that it is unknowable." It may just happen that the first planet you look at contains the penny. Extremely unlikely, but not implausible. But that is the way I see truth and falsity. They are independent of our knowledge.
At that point, we make a judgement call. Do we potentially spend countless time and money on something that is likely outside of our reach? I believe a large part of philosophy is figuring out what we should spend our efforts on pursuing in reality. If someone tells you to live a certain life, is that reasonable to do so? Should we fear death? How do we know things? Is it reasonable to search for that unicorn?
I don't agree, but I don't think we can resolve our differences. I think it's a question of values. I keep ducking into phone booths (What's a phone booth?) and slipping into my Pragmatism Man costume. Yes, it's true, I am a superhero. Motto - "If I can't use it, who gives a fuck if it's true? If I don't give a fuck if it's true, it's not true." Long motto. Lousy, foul-mouthed superhero.
Quoting Banno
Australian Pain-in-the-Ass Man's motto may be "Muddle on," but we Amurcan superheros are made of stronger, non-metric stuff.
Quoting Banno
Little known fact - the phrase "jumping in with both feet" was coined based on Caesar doing just that at the Rubicon according to Roman historian Quintus Fabius Pictor's account.
What is the difference between "dialectical" and "bivalently-framed?" Is it that with the dialectic, the goal is to reach consensus, while with bivalently-framed, we have to make a choice?
Quoting apokrisis
If I understand you correctly, I think I agree. I'm not a big fan of the idea of truth, but for most people interested in philosophy, it is one of the central questions. In this discussion, I'm trying to argue in terms of how the word is commonly used.
Quoting apokrisis
That's why I'm so attracted to pragmatism as a way of approaching the world. I am self-aware enough to see that has as much, or more, to do with temperament as it does with reason.
Quoting apokrisis
I am skeptical of bringing physics into metaphysical arguments. It's often a symptom of wrong-headed thinking. Is that there one of them "category errors.?" Quantum mechanics seems to be a prime candidate for this mistake. I don't think that's the case with you, but I don't get it.
I agree with this. Many people, including some in this discussion, do not.
Keeping in mind that I vastly underestimated how long it would take to find the rock/penny. Even in our solar system there are probably hundreds of rocky entities two kilometers in diameter or greater. Even if it's on earth, how long would it take to check. If it's in another star system, it would take decades at least to reach it. Unless someone invents faster than light travel, we couldn't ever reach most systems.
I say, at some point, when something becomes too difficult to verify, it loses it's truth value. That's the pragmatic view - If the truth of a statement has no possible impact on the world, it 1) has no truth value or 2) it is meaningless. Maybe those two are the same.
Sure. Truth is independent of knowledge. The statement "The capital of Botswana is Georgetown," certainly has truth value, even though you don't know if it's true. From a pragmatic point of view, who gives a s**t, and if no one gives a s**t, it ain't true.
I recognize many people disagree with this view. As Aristotle said, or was it Kant, "Hoo boy, metaphysics is a bitch."
I agree strongly. Turns out you're a pragmatist too. Welcome.
Yeah, nah. :smile:
Physics practices its own winning brand of metaphysical world-modelling. It gets on with what it believes works.
Philosophy of science might then critique that.
The difference is that we know that fictional entities we have created for our diversion are fictional entities; we know they don't actually exist. We have imagined the multiverse as a possibility; we have no way of determining if it is an actuality; which is to say we have no way of knowing whether the proposition 'the multiverse exists' is true or not. So, my question is as to whether we can even sensibly speak of the multiverse in terms of being actual or not actual.Intuitively, of course, it seems we can; but if that's right then we do think that untestable conjectures can be true or false. So we think they can be true or false, but can they really be true or false, or is that question incoherent?
Ain't metaphysical, by definition. Physics is not metaphysics, otherwise what would be the point of having a separate subject area? Metaphysics raises its head over the interpretations of what physics implies - many worlds, etc. Physics is 'shut up and calculate'.
Bivalence is a reduction to two options. That sets up the further reduction to just the one monistic choice - as the other becomes the not-true.
This is @Banno's pattern of thought. You can always tell a reductionist by the way they build their conclusion into their terminology. Determinism is opposed to in-determinism. Sense is opposed to non-sense. By this kind of rhetorical trick, they hope to reinforce the notion that truth is something monistic. You either see things their way or you are simply opting for the option that their jargon already negates.
The sign of dialectical or triadic systems thinking is that the poles of any metaphysical dichotomy each have their own name. A dichotomy is where both choices are "true" in standing as the positive limit of the other. One doesn't negate the other. Each negates the other. And what do you get from a double negative? :grin:
So instead of determinate vs indeterminate, it becomes determinate vs vague. You don't signal that one choice is wrong by pointing out that it is merely an absence of some particular metaphysical quality. You give both their own proper name.
A small point of jargon. But important where folk are mostly arguing rhetorically.
Anyway, the difference can be summed up that by saying the principle of bivalence is the logical claim that propositions are to be judged either true or false - true or not true. And a dialectical or dichotomous logic says that any "bivalent" division of metaphysical possibility has to obey the rule of being "mutually exclusive/jointly exhaustive". So to be "true", each has to stand as the logical negatation the other. Or to be more accurate, each has to be the formal inverse of reciprocal of the other.
So for example, vagueness is defined as that which is lacking all definiteness. And definiteness is that which is lacking all vagueness. But for each to have a measurable lack of the other, there must be that other to stand as a counterfactual possibility.
We are thus making statements about qualities being defined mutually "in the limit". A reciprocal relation.
Vagueness = 1/determinate. Determinate = 1/vagueness.
This is why a metaphysical dichotomy leads on to a triadic or holistic resolution - a Hegelian synthesis or Peircean semiotic. You have two things that exist as the third thing of their mutually co-dependent relation.
So when it comes to metaphysics as a historical practice, you can see how a division of thought might arise.
There are the reductionists who want to arrive at some monism and so they either proclaim the monisms of Idealism or Realism as "the one true path of all right thinking folk", or they get upset by paradoxes that arise and simply reject metaphysics as a discipline in its entirety.
The other path is the one that successful metaphysics has always taken since the ancient Greeks first developed the two general approaches to logical thought. And it is no surprise if logical holism might win the game. Nature is of course a cosmic whole. (Well, that is the general hypothesis that has worked out so far.)
Quoting T Clark
Pragmatism is logical holism. So you can pick it for that reason.
Reductionism is fine too. It works really well if you want to build machinery or even mechanise human society and the human mind. Simple cause and effect thinking is neat little everyday tool of thought.
But if you want to do metaphysics, you have to study metaphysics for the actual logic it employs.
Quoting T Clark
I don't see "metaphysics" as something beyond science. It clearly grounds science. And science then delivers a pragmatic judgement on the abductive speculations.
What do you think metaphysics ought to deliver as its social good? Does it have a purpose? I can't see any other reason to "do metaphysics" except to attempt to deduce the truth of reality from first principles ... and so set yourself up with clear hypotheses worth the effort of empirical test.
So pragmatism rules. Otherwise it is just spinning tales that make no difference.
The reason why quantum physics keeps coming up is that it simply destroys "reductionist privilege" at root.
You can cobble together a decoherent "maths of reality" out of a combo of wave mechanics and statistical mechanics. You can arrive at an effective collapse of the wavefunction - with only a last tiny grain of uncertainty or vagueness. But in the end, there is no closure, no actual wavefunction collapse. Monism loses. The irreducible triadicity of a holistic systems logic has to be accepted.
So metaphysics provides two general cultural models of reality - the reductionist and the holistic. They are both just models - good for their various applications. One is great for seeing reality as a causal machine. A mereology of parts. The other jumps to the other pole in seeing reality as an organic whole. The Cosmos becomes something quite "other".
This is just you boundary policing. Next you will be saying that Atomism played no part in the Scientific Revolution.
Did you have an example in mind?
They're all quite different philosophically, but they're all working from the same set of observations. So the differences must be those of judgement and interpretation - metaphysical, in fact. The physics is effective and predictable but what it means is open to all of these different interpretations.
Interpretations. That is the point. An observation of a physical phenomenon is just that - you register a measurement on an instrument, there's no room for disagreement about the reading. But what it means is wide open to interpretation.
Quoting T Clark
I don't see how.
That's because most physicists are not employed to speculate.
Quoting Janus
It's a devilishly difficult thing to understand, but as I understand it, it doesn't make 'the observer problem' go away.
Sigh. How is your case furthered by citing all these physicists taking different metaphysical positions?
They certainly ought to constrain what would be considered credible.
Like after Darwin, you might quarrel about how humans arose from apes. But no longer do you need to worry about the mechanics of turning ribs into first wombs.
It is one thing when the needle moves. It is another thing when a guy in a white coat told you it was going to move exactly like that for exactly this reason.
The situation is no longer “wide open” for interpretation. You have a job to do to say why some other interpretation would both predict the same thing and much more besides.
Well if you don’t understand the point there’s not a lot of use trying to explain it again.
With regards to the reading of the dial - there is a philosophical position called ‘instrumentalism’ but not everyone holds it. And the reasons that not everyone holds it can’t be found within physics.
Quoting Wayfarer
Did you understand your own point. Seems not.
Quoting apokrisis
Its models are mathematical formulations that are tested against observational data, but that is not an exercise in metaphysics. The disputes about the interpretation of quantum mechanics can be regarded as metaphysical but the practice of physics is not as it can be carried out without reference to any such interpretations.
So the metaphysical work gets done to set up the theory. It doesn’t follow the measurements as they already build in some metaphysical basis.
All I was saying is that however we might interpret QM the interpretation is a physical, not a metaphysical one, at least in the sense of not positing something transcendent at work. If by metaphysical all that is meant is ' something not directly observable", which might be better termed 'metaempirical' then fine.
Anything goes then?
If this is to be argument by definition, then I’m happy with the usual position that metaphysics is an inquiry into the nature and causes of being, Then as a debate, transcendence vs immanence is one of its familiar organising dichotomies,
Quoting Wayfarer
It isn’t me that wants to make a sharp distinction here. I take the opposite view. Science is how we put metaphysical reasoning to the test.
Really? It's an obscure bit of truth theorizing. Note the realists talk out of both sides of their mouths. :roll:
Maybe it just comes up in a lot of my discussions.
How can we talk about "multiverses" when multiverses are unknowable ?
It is the same problem that goes back to Kant's phenomenon and noumenon. Kant proposed that a phenomenon is a perceptive representation of an object existing in the mind of a perceiver, rather than the object in itself, the noumenon. Kant did not argue that the world of the noumenon does not exist, for there to be an appearance, there must be something for there to be an appearance of. It is just that human knowledge of the true nature of the noumenon is impossible, as the true nature of the noumenon is always mediated by the senses. In that, for example, we perceive the colour red, we don't perceive a wavelength of 700nm.
In this sense, all our beliefs are fictional, and every proposition we use is about a fictional object. When we ask, is the proposition "the multiverse exists" true or false, we are not referring to an unknowable entity in the world, but we are referring to a fictional entity "the multiverse". Similarly, when we ask, is the proposition "there is a table in front of me" true or false, whilst it is true that the parts that make up the table exist in the world and are knowable through the senses, the "table" as a whole, as a particular set of parts, only exists in the mind of the observer.
Therefore, complex objects such as "unicorns", "tables", "chairs", "mountains" and " multiverses" only exist in the mind in the imagination, and are therefore fictional. However, the fact that our all our beliefs are about fictional objects makes no pragmatic difference to our ability to exist within the world.
If I want a beer in a Tanzanian bar, all I need to know is to speak the symbol "bia moja tafadhali". I need know no more. I don't need to know the process of what happens between my speaking the symbol and my achieving my goal. The symbol "bia moja tafadhali" has no meaning in itself outside of any context it is used in. My speaking the symbol "bia moja tafadhali" in the context of a Tanzanian bar means that I will be given a beer. The symbol only has meaning within the imagination of the users, and is therefore fictive.
I may believe that "unicorns exist" is a fiction, but I don't know that unicorns don't exist. I may believe that "the multiverse exists" is a fact, but I don't know that multiverses do exist.
Even if unicorns, tables and multiverses must always remain unknowable, "unicorns", "tables" and "multiverses" can be knowable as fictive entities within the observer's imagination.
IE, in answer to your question, we can sensibly speak of the "multiverse", as what we are speaking of is a linguistic fiction, whether or not it is a fact in the world, and as a linguistic fiction can be either true or false.
I was going to say your analogy, comparing the multiverse to noumena, is not applicable, but I thought about it more. I think it is a good analogy. I started this thread to discuss things like the multiverse and my belief that, if I can't know, demonstrate, whether or not it exists, it's existence has no truth value or is meaningless.
I don't think you will find my solution to the issue satisfying - in my view, noumena don't exist either. They are just one way of looking at reality, similar to Lao Tzu's Tao and in contrast to the idea of objective reality.
Would it make more sense to you if I changed "values" to "preference" or "taste?"
I'm not sure "rhetoric" is the right word. They're not just trying to convince you of their position, they actually believe in the truth of what they say and are trying to present their position.
Quoting apokrisis
That would be true if they make a positive and open minded argument for it. No problem there.
I posted this before I was finished by accident. Let's try again:
Although I agree with your point about how bivalence works, I think there is a place for it as long as you recognize that it is just a point of view, a choice, and not the fundamental basis of reality. I guess that's what you mean when you say:
Quoting apokrisis
Quoting apokrisis
For me, there is no "truth of reality." There are lots of ways of seeing reality. You can choose the one that's most useful in a particular situation, then switch to a different one when the situation changes. I see philosophy, metaphysics, as a tool box. Pull out the right tool for the job.
These are always “just models” that need to prove themselves pragmatically.
And I’ve said that reductionism and holism themselves are reciprocal points of view - a dichotomy - if understood correctly. I don’t reject one in favour of the other, but do then use each to sharpen the sense of the other.
You could consider that a disputable meta-metaphysical claim. I would be quite happy to defend it.
I think you and I are in agreement.
I think there must have been some misunderstanding. You seem to have said that the truth value of the sentence given in my post is a question of taste. But that makes no sense. So you've lost me.
But how else to read this:
Quoting T Clark
You wrote:
Quoting Banno
I say - Whether or not you want to assign truth value to the referenced sentence is a matter of your choice, taste, value, preference. It's not a matter of fact. I, when I'm wearing my pragmatist boots, would say no. That would be a matter of my choice, taste, value, preference.
Whether or not you agree with that, it shouldn't be hard to understand.
Quoting T Clark
There's something very odd happening here.
One more try, perhaps. You asked:
Quoting T Clark
I responded with:
Quoting Banno
...pointing out that whether one assigns true or false to this sentence, it must be undecided, and hence it is a candidate for an example fo the sort of sentence you asked for.
There's nothing here about taste. Whichever you assign, true or false, the sentence is undecided.
Actually, on looking at it again, I wonder if we might do better. Consider my other suggestion:
Quoting Banno
Assume a bivalent logic. Then this statement is either true or it is false.
If it is true then it is undecidable.
If it is false, then the antecedent is true, hence "it is not possible to determine that this statement is true" is true.
So in either case it is undecidable.
Quoting TheMadFool
Not unlike a Godel sentence, but with "decidable"" in the place of "provable". Where a Godel sentence is true but unproven, this sentence is presumably either true or false, but we can't decide which.
If something's truth value is undecided that doesn't mean it isn't true or false, only that I don't know. On the other hand, if it's truth value is undecidable, I consider it either as having no truth value or as being meaningless.
I think we've gone far enough with this. I don't see that any more back and forth will bring us any closer to agreement.
Yep.
Quoting T Clark
Fine.
Quoting T Clark
I answered your question and you get all huffy. Odd. OK, that'll do.
It's not so much argument by definition as it is a recognition that physics is not concerned with the transcendent (whatever that might be thought to be). Whatever physics is concerned with it is based on what has been observed or hypothesized based on the math. I don't see how "transcendence vs immanence" is relevant to debates about interpretations of QM.
We can talk about the multiverse because it is imaginable. I'm not sure whether you are referring to the cosmological hypothesis that our universe may be one "bubble" of spacetime among an infinitely numerous array of others, or the MWI explanation of the collapse of the wave function.
It doesn't matter anyway because either is imaginable as a possibility, but both would seem to be impossible to confirm or dis-confirm. The question is whether, since we cannot know the truth regarding these speculations, we should think they therefore cannot be true or false.
You say they are fictional, but we don't know that, because that would be to know that they don't exist. You could say that they might as well be fictional, since they cannot exist for us.
I was reading somewhere recently that some astronomers think it may be possible to look for evidence of multiverses associated with cosmic inflation by looking at anomalies in the cosmic microwave background. Can't remember where I saw that.
Quoting Janus
This is ridiculous. Here is what a competent philosopher says as something just taken for granted….
Quoting Janus
Discussion would be much better if you bothered to read what I wrote, rather than jumping to stupid conclusions about what I'm saying.
Be huffy. But as Callender notes, it is not about what is or isn’t observed. The metaphysics grounds what even counts as the right kind of measurement.
If you feel your preferred jargon covers that, go for it. But it would be nice if you could supply a source to substantiate your implication that metaphysics and “metaempiricism” ain’t just synonyms here.
There is a lot of "New Age" thinking that would seek to use the "observer problem" as justification for the notion that mind is, in some way apparently no one is able to coherently imagine, the foundation of reality.
That is a supernaturalist view, or an anti-naturalist view, if you prefer; it is the idea that there is a higher realm of mind or spirit that gives rise to what we, "down here", understand as a physical reality.
But who supports a definition of metaphysics as the study of the supernatural?
And when metaempirical is used as a term, it is about the wider epistemic reasons for believing in a theoretical framework rather than about the ontological presumptions that might motivate ideas about suitable experimental metrics.
So metaempirical justification for some line of physical inquiry might be Occam’s razor, or this way of thinking has worked for us before, or this way of thinking seems to produce more results than just the ones we were directly aiming for.
Metaphysics is indeed a broad brush label. But context would make it clear I was talking about ontic presuppositions that lay the ground for the actual business of making measurements. So for instance, whether you believe reality is made of particles or waves, whether you believe actions are local or nonlocal, etc.
The fact that New Age crackpots conflate two kinds of “mystery” - quantum collapse and the neuroscience of consciousness - is just one of those things. It has nothing to do with metaphysics and science as two fruitfully related academic disciplines … if you must treat them as clearly demarcated in the first place.
My vote: just spare us from the crackpots and their theories that can’t even past the first hurdle of “even being wrong”.
I understand that, but my point is that you cannot make any progress in answering the question if you are not clear on the criteria that the answer should satisfy. Without that the question is effectively meaningless (as you like to say).
Take interpretations of quantum mechanics, for example:
Quoting T Clark
Meaningless for you, because of the particular epistemic criteria that you set out for yourself in this case: if you can't put a proposition to an empirical test, then it is meaningless. (Not so for others, so they must be applying different criteria.)
Now, in the OP you want to turn the question onto that epistemic criterion itself. But that's clearly inapt: an epistemic criterion is not the sort of thing that you can test by the methods of science. You can see if it leads to contradictions or to unpalatable conclusions, but that's not the same thing.
My belief, along the lines of Kant's phenomenon and noumenon, is that all understanding we have of complex objects in the world is fictive, whether "unicorns", "tables" or "multiverses".
However, even if our understanding of complex objects in the world is fictive, this is independent of the question as to whether such complex objects as unicorns, tables and multiverses actually exist as facts in the world.
I know that I have the subjective experience of colours. I believe that you also have the subjective experience of colours.
I can never know that you have, and I can never demonstrate that you have, but for me, the possibility that you have a subjective experience of colours has both a truth value and meaning.
The truth value is that the proposition "T Clark has the subjective experience of colours" is either true or false.
As regards meaning, the fact that you can or can not have the subjective experience of colours has meaning to both you and me.
IE, unprovable beliefs have both a truth value and meaning.
So it's a completely vacuous statement, but also misleading, since originally you singled out multiverses in particular as fictional.
Far be it for me to say that the multiverse doesn't exist.
If we can never know whether the multiverse exists or not, even in principle, then we can only know the multiverse as a fictional entity, even if the multiverse does exist as a true fact.
Quoting SophistiCat
I think you are really saying the same thing I am, just using different language. I say "metaphysics" you say "different epistemic criteria." The epistemic criteria you use is what Collingwood would call an absolute presupposition. Different people in different times doing different work use different absolute presuppositions. I never claimed that my particular way of seeing things has some priority. I've said the opposite in fact.
Quoting SophistiCat
Exactly. As I've said over and over, it's not science, it's metaphysics. It has no truth value. It's something we choose, usually unconsciously.
Comparing the multiverse to the experience of color is not a good analogy. There is strong evidence that I experience the color red. When you hold up a card colored red, ask me what color it is, and then I say red. When my brain lights up in a red way on the MRI. That's all evidence, whether or not you want to say it is not absolute proof.
When I see someone cry out when they've been injured, crying and holding their arm, do you doubt they feel pain? They'll tell you they are. They'll act like they are. They act like I do when I experience pain. If you were to put someone in pain in an MRI, I think their brain would light up the same way mine does when I am in pain. We're built the same, mechanically, anatomically, physiologically, neurologically, psychologically.
Then you'll want to talk about P-zombies which... Well, no we won't go there.
I was watching a television news show a few years ago. They were showing how MRI technology was starting to be used to read minds. They would show someone pictures while in the device. After they had built up an MRI "vocabulary," they would show the same pictures to someone else. Based on their vocabulary, they could tell when they were looking at the same pictures as the previous subject.
Previously you used the term 'fictional', which means imagined, now you have changed to 'fictive' which has different, although related, connotations, for me at least. (Perhaps I should look them up in the fictionary). As far as I know Kant does not claim that our understandings of empirical objects are either fictional or fictive, and I'm really not sure what you are trying to get at.
Quoting RussellA
So are you claiming that facts are ficts, and that the difference between tables and unicorns is that one is a fict or fact in the world and the other a fict or fact in an imagined world or something like that? Is the world also fictive for you?
(As an aside, there is a philosopher, Markus Gabriel, for whom the world does not exist, since to exist is to exist in a world; or as he terms it "field of sense", and the world does not exist in a world, else there would be an infinite regress. 'The world; is just a placeholder for the sum of all possible fields of sense for Gabriel, if I have understood him correctly).
The MRI scanner can make measurements of your brain when you look at the colour red, but can the MRI scanner determine that you are experiencing what Chalmers calls the "qualia" of the colour red and others call the subjective experience of the colour red ?
To save you having to look words up in the dictionary, both fictive and fictional are adjectives describing literary ideas created by the imagination, ideas that are unreal or untrue.
However, fictive is more creative, or more imaginative, than fictional, as in the fictive world of Blade Runner and the fictional world of Around the World in Eighty Days.
I have two responses.
First, most people on the forum here don't accept personal experience as evidence. A good example is reported personal experience of God. Based on that, there is no evidence at all for qualia, so, yes, it is a metaphysical property or meaningless. No, I don't believe that.
Second, the whole "hard problem of consciousness" is a made up problem. Consciousness is a mental process. Mental processes grow, emerge I suppose, out of brain processes the way life emerges out of chemistry. What's the big deal? No, I don't want to get into a discussion of the hard problem of consciousness here.
Quoting RussellA
You keep going back and forth between calling everything in our experience and imagination fictional (thus rendering the claim vacuous) or specifically those things that we cannot empirically verify (thus merely misusing the word 'fictional'). What's funny is that what you refer to as 'noumenon' is real according to the first criterion (as opposed to the 'phenomenon') and fictive according to the second.
I would say that anything that you are capable of affirming or denying perforce has a truth value, and not just those things that can be scientifically verified.
In any case you haven't addressed the point of my response which was that we don't simply imagine the things in the world in any way analogous to how we imagine the things of our literary fictions.
Your previous statement was "There is strong evidence that I experience the color red. When you hold up a card colored red, ask me what color it is, and then I say red. When my brain lights up in a red way on the MRI. That's all evidence."
Your new statement seems contradictory to your previous statement.
Your new statement seems to say that there cannot be evidence for what may be called "qualia".
Your previous statement seems to say that there can be evidence for what may be called "qualia"
Not quite.
Taking a table as a particular example of "everything in our experience". Our understanding of what a table is may be fictional, without rejecting the idea that there are facts in the world which we think of as a table. The word "fictional" retains meaning, as fictions in the mind are set against facts in the world.
Quoting SophistiCat
Not quite.
Our concept of complex objects, such as a table, is a fictional interpretation of facts in the world. Our knowledge of facts in the world derives from empirical observation of the world discovered through our five senses, such as a screeching noise, the colour red, a sweet taste, an acrid smell, the pain of a needle. Our imagination assembles these parts into a whole. Each part, a particular sensation through one of our five senses, directly comes from a fact in the world through empirical observation. The whole, our concept of a table, is a fictional assembly of mereological relations between these parts.
Quoting SophistiCat
Kant did not argue that the world of the noumenon does not exist, for there to be an appearance, there must be something for there to be an appearance of. In Kantian philosophy, a noumenon is a thing as it is in itself, as distinct from a thing as it is knowable by the senses through phenomenal attributes.
There are things in the world, and as facts in the world they are real. But, our understanding of complex objects, such as tables, which are assemblies of things in the world, is fictive.
I am trying to be careful in distinguishing complex objects, such as "unicorns", "tables" or "multiverses" from simple empirical experiences through our five senses, such as a screeching noise, the colour red, a sweet taste, an acrid smell, the pain of a needle.
This is why I previously wrote: "My belief, along the lines of Kant's phenomenon and noumenon, is that all understanding we have of complex objects in the world is fictive, whether "unicorns", "tables" or "multiverses""
I believe that our understanding of complex objects, such as a table, is as fictional as our understanding of Sherlock Holmes, but this does not include our experience of simple sensations, such as the pain of a needle, through the five senses.
There are nineteen uses of the concept “noumenon” or its derivatives in CPR. None of them equate noumena with the ding an sich.
I have no argument for how you personally wish to think of noumena; the idea has been tossed helter-shelter for centuries. I’m merely calling attention....rhetorically at that.....to a conflict with the stated reference.
At the end of the statement you quoted it says "No, I don't believe that."
I didn't know of the debate about how a noumenon relates to a "thing-in-itself". More reading to do.
A relevant paragraph in Critique of Pure Reason is:
"The concept of a noumenon, i.e., a thing which is not at all to be thought as an object of the senses, but rather only as a thing on its own (solely through a pure understanding), is not at all contradictory, for we still cannot assert of the sensitivity that it be the single, possible manner of perspective."
Rather than writing "In Kantian philosophy, a noumenon is a thing as it is in itself.", perhaps I should have written "In Kantian philosophy, a noumenon is a thing on its own".
It’s all the Good Professor’s fault. He took care to say exactly why and how he wanted noumena to be understood (A249/B306), in accordance with a brand new approach to metaphysics in general, then proceeded to make it seem like not that. So people fall back on, “See? Toljaso!! He said ‘the thing-in-itself (noumena)’, right there!!!” (B315).
As to the debate, the whole thing boils down to.....understanding did something, while not contradictory, yet for which it had no proper authority. The text subsequently makes clear that noumena have no legitimacy in the metaphysical nature of human cognition, the debate itself grounded in noticing the former and disregarding the latter.
————
Quoting RussellA
According to the text, the best to be done along those lines is, noumenon is that which understanding thinks on its own.
1. What is x? [not a statement; ergo, can't be true or false]
can be rephrased as
2. x is p OR x is q OR x is r OR x is...[a statement; ergo, can be true or false]
Metaphysical statements
An example:
3. God exists Or God doesn't exist [we don't know; we cannot know; nevertheless, a statement that can be true or false]
can be rephrased as
4. Does God exist? [not a statement; neither true nor false]
:joke:
One of my favorite philosophers.
Perhaps the most commonly referenced one ever.