Transparency and reflection exist only in the depth of the dimension of a visual image.
The impression of the transparent medium is that something lies behind the medium. A completely monochromatic visual image cannot be transparent. — Ludwig Wittgenstein
It seems that if everything in the world were just as it is now, but transparent, we would be able to see what is beyond the world. — Amalac
Just as a burning coal (around 1500 K) glows red, and a hot bright star (around 6000 K) glows yellow or blue, the CMB glow with a characteristic colour associated with it’s temperature. However, because it is so cold, the light which was emitted by the glowing Universe now has a much longer wavelength than we can see with our eyes. The CMB is brightest at a wavelength of around 2 mm, which is around 4000 times longer than the wavelength of the visible light we see with our eyes.
Everything is pretty much transparent. — fishfry
Let's use this definition of “transparent”: such that through it some other object that is both not transparent and not translucent can be seen with clarity. — Amalac
Transparency and reflection exist only in the depth of the dimension of a visual image.
The impression of the transparent medium is that something lies behind the medium. A completely monochromatic visual image cannot be transparent. — Ludwig Wittgenstein
But anyway, let me phrase it in another way: The window of your house looks like what can be seen through it, right? So then, how would it look like if the only objects that were in the world were other windows just like it (and where spaces were also transparent in the sense I described)? — Amalac
If everything in the world was transparent, you'd see the CMB. — fishfry
The CMB is not transparent, but would you agree that it was logically possible for it to have been transparent? Or do you disagree with this? — Amalac
It's not logically possible for the CMB to be transparent, because its existence is a consequence of our best theories of physics AND it's been seen by experiment. — fishfry
Ok, but we're talking about possible worlds. It may be physically impossible for the CMB to have been transparent, but if we say that it is logically impossible for it to have been transparent, that means that the idea of a transparent CMB would have to entail a logical contradiction (as in: there is no possible world in which the CMB is transparent). In that case, what is the contradiction? — Amalac
As Wittgenstein pointed out in his “Remarks on color”, in the context of philosophy he doesn't use terms like “transparency” in the sense in which they are used by physicists, rather in the sense we use those terms in ordinary life. He adds later that he is not looking for a physical theory of color, but rather on the logic of color, or the logic of color concepts. And here I'm looking for the same thing. — Amalac
Possible worlds (you mean David Lewis or physics multiverse?) — fishfry
One of the most characteristic features of that (Leibniz's) philosophy is the doctrine of many possible worlds. A world is "possible" if it does not contradict the laws of logic. — Bertrand Russell
Like I say, what color would you like it to be? If you're talking possible worlds, I suppose there's a world where there's a transparent CMB and behind it a background of rainbows and unicorns. Who can say otherwise? — fishfry
It seems to me that you are missing the point of the experiment. — Amalac
In that possible world, absolutely everything would have to be transparent, and if there were something behind the CMB, then whatever was behind it, being a part of the world, would also be transparent, and if there something beyond it would also be transparent and so on ad infinitum.
Let's suppose that there some ultimate boundary of the universe, beyond which there is nothing, not even empty space (i.e. the universe is finite with regards space). Then I ask: Is it logically necessary that this boundary is not transparent? (Otherwise we would see “nothing” if we looked at it, no colors at all)
And let's suppose that the universe were infinite with regards space, how would it look like if absolutely everything was transparent? — Amalac
And what if I say that rainbows and unicorns are logically necessary? — fishfry
If rainbows and unicorns were logically necessary, then their non-existence would imply a logical contradiction. But obviously that's false: no logical contradiction arises from denying their existence, since they are, in that sense, contingent (as Leibniz would put it: it would be logically possible for them not to exist).
When asking: Was it logically necessary that not everything in the world was transparent? I ask: Does the existence of such a world involve a logical (not physical) contradiction? If so, what is the contradiction? — Amalac
If 2 + 2 = 5 — fishfry
then I am the Pope — fishfry
If 2 + 2 = 5
— fishfry
There is no possible world in which 2+2=5 — Amalac
p→q is equivalent to: not p or q, so “If 2+2=5 then I am the Pope” means: Either 2+2≠5 or I am the Pope, which is true because 2+2≠5. The paradoxes of material implication only arise because they contradict the way we use them in ordinary life, to logicians they don't pose any problems if we interpret them as not p or q. But at any rate, material implication has nothing to do with my question. — Amalac
If 2 + 2 = 5
— fishfry
There is no possible world in which 2+2=5
— Amalac
How do you know? — fishfry
But I would like to ask you, besides mathematics, can you name a necessary truth? I mean one that's not trivial, such as that "if all men are mortal and Socrates is a man then Socrates is mortal." Can you name a meaningful proposition that is logically true, necessarily true in "all possible worlds," that doesn't rely on math? — fishfry
The claim that "the CMB is transparent" is factually false, so anything at all follows from it. That's my reasoning. — fishfry
Now about these other worlds. For one thing, the CMB is the boundary of the observable universe. I imagine you might be inclined to grant that this is a necessary truth. In which case, if it's transparent, we still can't see past it. So we'd see black. Necessarily, because by definition we can't possibly see past the CMB. — fishfry
But if the CMB is transparent, then we're in a world with different laws if physics. In which case, why might there not be different laws of mathematics or logic? — fishfry
6.375 As there is only a logical necessity, so there is only a logical
impossibility — Ludwig Wittgenstein
Technically I don't, but I thought you would just take this for granted. I mean, you can take the extreme sceptic route of doubting that 2+2=4 is true in all possible worlds, but that would just dispose of mathematics and logic altogether, and I doubt that's your aim. — Amalac
A world where 2+2=5 is inconceivable. — Amalac
If you have 2 oranges and 2 other oranges, how could you possibly not altogether have 4 oranges? — Amalac
2+2=4 is analytically true, just as “a bachelor is an unmarried man” is: it follows from the definition of 2+2. Perhaps you could doubt this, as Kant did, by saying that 2+2=4 is in fact synthetic. But even Kant did not doubt that 2+2=4 is a priori true. — Amalac
All analytic propositions are necessarily true, because the predicate is contained in the notion of the subject. All analytic propositions are trivial because of that (and yet they are still meaningful). — Amalac
Then there is of course the famous debate between empiricists and rationalists, as to whether we can have knowledge about the world that can be obtained by mere reasoning, without the aid of experience. — Amalac
What I asked in the OP was if there could be statements which are true about the world, but which are known a priori (Such as: If the universe has a boundary, then such a boundary must not be transparent when seen by a human by logical necessity, since it is impossible for a human to see anything that does not have any color, in the sense in which black and white are also colors). — Amalac
Immanuel Kant, for instance, held that the Law of causality was synthetic (not analytic), but known a priori. And the Law of Causality, if true, would give us knowledge about states of affairs that we have not yet experienced (a priori knowledge about the world). — Amalac
This here is maybe where you are going off the rails: I'm not claiming that this is the case, I'm asking if it is even possible for the boundary of the universe to be transparent, as in: could this be known by mere analysis of the concepts of “transparent”, “seeing”, “universe”,etc? Or is it a synthetic proposition that is nevertheless still a priori true, just as Kant held the Law of Causality to be? — Amalac
In that case either: it looks black because there is something black beyond it, which contradicts the idea that nothing could be beyond that, or it looks black because it is black. But then it's no longer transparent (in the sense I gave in the OP), since as Wittgenstein pointed out something transparent cannot look monochromatic. This contradicts the definition of that possible world (as in: we would in that case no longer be talking about that possible world, but rather about some other possible world), so it too can't be the case. — Amalac
It may in that case still be transparent as the word is used by physicists (in the sense that it let's X kinds of light to pass through, despite looking as if it were opaque), but not in the sense that you can see through it. — Amalac
But even ignoring that, if by definition that is so, could we then say: “The CMB (or the boundary of the world) is not transparent (in Wittgenstein's sense)” is an analytically true proposition that nonetheless gives us knowledge about the world? — Amalac
Because then we would not be talking about possible worlds, since a possible world in Leibniz's sense is one which does not contradict the Laws of logic. — Amalac
So, if that world is a possible world, then it can't possibly have different laws of logic, since otherwise it would not be a possible world. And if you accept that mathematics is a prolongation of logic, then the truths of mathematics also cannot be different (although this second claim about math being an extension of logic is far more controversial): — Amalac
As someone who finds the doctrine of possible worlds incoherent, I don't see why logic and math couldn't be different in some alternate world, just as physics is. I agree I can't conceive of it, but who made me the authority on such things? — fishfry
I could say, if the CMB is the remnant of the big bang, how could it be transparent? But we'd be arguing nonsense. — fishfry
We are not doing physics here(...)
(...)The question is: how does our visual image have to be, if it is to show us a transparent medium? How, e.g., does the medium's color have to appear? Speaking in physical terms - although we are not directly concerned with the laws of physics here - everything seen through pure green glass should look more or less dark green.
(...) That is not a proposition of physics, but rather a rule for the spatial interpretation of our visual experience.
But if the CMB is leftover radiation by definition, how can it be transparent? It always has some small but nonzero color temperature. — fishfry
But I am not convinced that physics is contingent either. I wonder if anything is contingent. In some logically possible other world, Socrates was a bricklayer and not a philosopher. But what other things would have had to change? You'd have to drill that down to his ancestry and environment and life experiences. I don't think I have enough imagination to believe in contingency at all. Today I'm wearing my determinist hat. Socrates was destined to be a philosopher from the moment of the big bang. — fishfry
3.0321 We could present spatially an atomic fact which contradicted the laws of physics, but not one which contradicted the laws of geometry. — Ludwig Wittgenstein
Do you believe there's a possible world in which Einstein's famous prediction failed and Newtonian physics reigns supreme? — fishfry
No amount of philosophical theorizing could possibly give us knowledge of the actual world. — fishfry
Is a perfect window colorless? — fishfry
if you stack up enough windows you'll see that window glass is actually usually a blue/green color. It's just so translucent that with only one pane it's pretty much impossible to see
So you have to say what you mean by transparent — fishfry
But if the point is that a perfect window has no color, I suppose I can agree with that. — fishfry
Everything is pretty much transparent — fishfry
You nailed it. It all depends on what kind of energy we're talking about. A masonry wall is transparent to sound though not to visible light. Walls are also transparent to radio-waves, X-rays, gamma-rays. You get the idea. — TheMadFool
My point was more like: If the universe has an edge, then such an edge must not be transparent by logical necessity (not merely physical necessity), because otherwise we would be able to see what is beyond the universe. — Amalac
The argument would be: anything we see is part of the universe. Therefore, if we could see something through it, that thing would be both in the universe and beyond the universe, which is absurd. Therefore, it's impossible for there to be anything beyond the edge of the universe (in an all-encompassing sense, not in the sense some physicists speak of “multiverses”). — Amalac
And yet, if nothing could be seen through the transparent object, then the transparent object would not have any color when we looked at it. But that's also absurd: since we impose color onto all that we perceive, it's impossible for us to see something that has no color. — Amalac
Therefore, in view of the 2 previous conclusions, we conclude that it is logically necessary that such an edge is not transparent/translucent. — Amalac
Well, the doctrine of many possible worlds is just taken for granted in modal logic, for example. ]/quote]
I'm saying the whole idea is incoherent to me, notwithstanding all the smart people to whom it's coherent. I'm just not one of those smart people.
— Amalac
When saying X is logically possible, all one means is that the existence of X does not violate any of the laws of logic. That's just the definition of a “possible world”, there's nothing incoherent about it. When asserting that there is some possible world in which X exists, one does not assert that such a world literally exists in some alternate reality (at least most people don't), rather one merely asserts that reality could have been that way, or could be that way, depending on what the assertion is. — Amalac
But then you are doing physics again, while I'm trying to do logic. This seems to me like a case where you are confusing one language game with another. — Amalac
For example, Wittgenstein said this in his Remarks on Colour:
We are not doing physics here(...) — Amalac
As you yourself pointed out before, a universe where the CMB were transparent would have different laws of physics, and there is at first no logical impossibility in it having laws which would allow it to be transparent, not until you start considering what that logically entails. — Amalac
Again, is there some possible world in which the CMB had the necessary physical properties to be transparent, or were the Big Bang happened differently? Yes, so long as that does not involve a logical contradiction. That's all the doctrine of many possible worlds asserts. It does not claim that there are in fact alternate realities or multiverses, one in which that's the case (at least most interpreters of the doctrine don't, it seems to me). — Amalac
I mean, it's quite simple in a sense: I can imagine/conceive that if I jumped of the roof of my house I started floating upwards instead of falling. I can imagine/ conceive of the sun not rising tomorrow, and these events imply that physics is contingent. And since I can conceive of them, they are possible, they involve no contradiction. — Amalac
On the other hand, I can't conceive of me counting one orange, and then only another orange, and then somehow having altogether 50 oranges (1+1=50), because that contradicts the most fundamental and most self-evident axioms of mathematics. I can't conceive of seeing something that both was and was not a tree (at the same time and in the same sense), because that would violate the Law of Contradiction. — Amalac
3.0321 We could present spatially an atomic fact which contradicted the laws of physics, but not one which contradicted the laws of geometry.
— Ludwig Wittgenstein — Amalac
However, supposing one takes the route of determinism, then I ask: Do you agree with Leibniz's Principle of Sufficient reason as interpreted in his esoteric system, according to which every true proposition is analytic, including empirical truths? If so, I suppose there's no sense in arguing with you about possible worlds in which the laws of physics were different. — Amalac
To answer that we need to answer the question: Does such a state of affairs (a possible world in which Einstein's famous prediction failed and Newtonian physics reigns supreme) involve a logical contradiction? If it does, then there is no possible world in which that's the case. If it does not, then there is such a possible world. — Amalac
It seems clear to me that such a scenario does not involve or imply a logical contradiction, but if you think otherwise, then tell me what the logical (not physical) contradiction that such a scenario implies would be. — Amalac
Would you say this proposition does not give us knowledge about the world then?:
If the universe has a boundary, then such a boundary must not be transparent when seen by a human by logical necessity, since it is impossible for a human to see anything that does not have any color, in the sense in which black and white are also colors. — Amalac
Notice that assuming that the universe were in fact finite with regards space, then we could have knowledge about the boundary from the truth of the proposition above, without the need of experience (such as the experience of observing the boundary), merely by logically analyzing the meanings of words. — Amalac
And although in that case it would be perhaps considered an analytic proposition, nonetheless it seems to gives us knowledge about the world. — Amalac
Well, that's not the question but it is related to it somewhat. I would like to confirm: if a clear glass window (which according to physics apparently does have a color: blue) was in a world were the only other objects in it were other transparent objects, then is it correct to say that they would all look monochromatically blue? — Amalac
Some reddit user answered the question about what color is a window:
if you stack up enough windows you'll see that window glass is actually usually a blue/green color. It's just so translucent that with only one pane it's pretty much impossible to see — Amalac
And apparently the same is true for clear water: — Amalac
But that is relevant for the physics definition of transparent. I am using a different sense of that word, the one most commonly used in ordinary life by ordinary people. — Amalac
I did in my OP: such that through it some other object (at least one object) that is both not transparent (not transparent= such that you cannot see through it with clarity) and not translucent can be seen through it. — Amalac
t of that definition is that it is not a physics definition of «transparent», but rather one which defines the word according to our visual experience. — Amalac
If a window would indeed look monochromatically blue/green if it was surrounded only by other windows, then the average person who is not knowledgeable about physics would not call it transparent in the sense I gave in the OP. — Amalac
They would not be wrong, they would in that case only use the word with a sense that is not the physicists' sense (the meaning of a word depends upon its context, and the way it's used in a particular language game, as Wittgenstein would put it). — Amalac
I don't think I agree. The edge of the observable universe is as far as we can see. It doesn't matter what's beyond it. We can't see it in any event. It would appear black I assume. — fishfry
Space and time appear to be infinite in extent, and infinitely divisible. If we travel along a straight line in either direction, it is difficult to believe that we shall finally reach a last point, beyond which there is nothing, not even empty space.
But as TheMadFool notes, it's not transparent to heat, sound, etc. What exactly do you mean by transparent? Bats can detect windows by echolocation. To a bat, a window is not transparent. So you need to "define your terms" as they say. — fishfry
David Lewis claims possible worlds are real. That, I find clinically insane. — fishfry
But you didn't address my question about non-Euclidean geometry. Is there a world where Euclidean geometry holds (Newton) and one where it doesn't (Einstein)? There are a lot of technical problems with that belief. — fishfry
I'm saying the whole idea is incoherent to me, notwithstanding all the smart people to whom it's coherent. I'm just not one of those smart people. — Amalac
Those are of course physically made, imperfect window. I have for several posts already stipulated to a PERFECT window. You could have one ten miles thick and it would be perfectly transparent to visible light. — fishfry
You're going quite far afield now. What the average person would see of the real world is irrelevant to your point. — fishfry
Humans or bats? Human eyes or radio telescopes? Cameras or sonar? Cameras or radar? You haven't defined transparency at all. — fishfry
There is no Newtonian possible world, except in our imagination. It would make a fun science fiction story, but NOT serious philosophy. — fishfry
I already told you I'm talking about Leibniz's doctrine of possible worlds, not Lewis' strange claims (if he does in fact claim what you say he does, which I don't know). I don't agree with Lewis, I don't believe “possible worlds” (other than the actual world) exist. — Amalac
Modal realism is the view propounded by David Kellogg Lewis that all possible worlds are real in the same way as is the actual world: they are "of a kind with this world of ours."[1] It is based on the following tenets: possible worlds exist; possible worlds are not different in kind from the actual world; possible worlds are irreducible entities; the term actual in actual world is indexical, i.e. any subject can declare their world to be the actual one, much as they label the place they are "here" and the time they are "now".
I did address it, I said if there is nothing logically contradictory about a world where Euclidean geometry holds or one where it doesn't, then by definition they are both possible worlds. If you are going to say that there is no possible world in which Euclidian geometry and newtonian physics are wholly true, then that must mean that their truth implies a logical contradiction, in which case you just have to tell me what that logical contradiction is. — Amalac
Perhaps you could say that Euclidian geometry contradicts some basic axiom of mathematics or logic, in which case there are no possible worlds in which that's the case. — Amalac
If you are asking: Assuming that the current laws of physics don't change in the future, is there any possible world in which the whole of newtonian physics is true? Then the answer is no, since as you pointed out newtonian physics were, at least partially, falsified by observation. — Amalac
But the thing is, logic is not limited by the laws of physics. — Amalac
When saying that there is some possible world in which newtonian physics is the case, what one means is that we can conceive of a world where newtonian physics wasn't ever falsified, and in which the behavior observed that falsified newtonian physics simply didn't happen. That's possible, since there is nothing logically selfcontradictory about such a state of affairs. But then you may still go back to determinism and deny this. — Amalac
You say I'm just making you repeat yourself, yet you have asked me the same thing again about newtonian physics. — Amalac
Well, I simply don't agree with you in the least about what you say here, so there's no point in discussing the matter of possible worlds further. — Amalac
There's no common ground. Perhaps the Stanford Enciclopedia of Philosophy can do a better job than I did: https://plato.stanford.edu/entries/possible-worlds/ — Amalac
Ok then, if that's what you meant by “perfect window” then there are no problems. I accept that definition. — Amalac
It's not irrelevant, I was trying to clarify what I meant by “transparent”: When the average person speaks about X object being transparent, they probably have in mind something very different than what physicists have in mind. When saying «a window is transparent», they usually don't mean that it lets X,Y or Z amount of light To pasa through, they mean simply: you can see through a window. — Amalac
To quote Wittgenstein again: The meaning of a word is its use in a particular language game. The language game of describing things in daily life is not the same as the language game that results from doing physics. — Amalac
Human eyes. Have I defined it well enough for you now? — Amalac
So modal logic is not serious philosophy according to you? I disagree — Amalac
Ok, but I'm not talking merely about the observable universe, I'm talking about both the observable universe and the parts of the universe we have not observed yet (that's why I said I meant “universe” in an all-encompassing sense). — Amalac
I use the term in the same sense as the one suggested by Bertrand Russell in this passage:
Space and time appear to be infinite in extent, and infinitely divisible. — Amalac
If we travel along a straight line in either direction, it is difficult to believe that we shall finally reach a last point, beyond which there is nothing, not even empty space. — Amalac
Again, I don't use the word “transparent” as it is used by physicists, but rather in the sense Wittgenstein uses it in my OP. You can substitute “see through” (meaning: such that you can see through it) every time I say “transparent” if you like. I guess it's a sense more akin to phenomenology than to physics. — Amalac
At any rate, what is wrong with this definition of transparent object?:
An object such that when a human sees it, through it some other object that is both not transparent and not translucent can be seen with clarity. — Amalac
Modal realism is the view propounded by David Kellogg Lewis that all possible worlds are real in the same way as is the actual world: they are "of a kind with this world of ours."[1] It is based on the following tenets: possible worlds exist; possible worlds are not different in kind from the actual world; possible worlds are irreducible entities; the term actual in actual world is indexical, i.e. any subject can declare their world to be the actual one, much as they label the place they are "here" and the time they are "now". — fishfry
There are things that are logically possible yet still not possible. I'm not sure if there's a name for that position but if there is, that's what I am. I'm curious about that now. Maybe I'll google around. — fishfry
We can have no possible information about the part of the universe we can't observe. For all we know, in the unobservable universe, bowling balls fall up. There, I just contradicted my own position on this matter. — fishfry
I agree with you in this point, that sounds insane. — Amalac
Good! If I got you curious about something, then our exchange about possible worlds wasn't entirely fruitless. — Amalac
I mean the part of the universe we can't observe at present, but may be able to observe in the future. We may never see those parts, but it's not logically impossible to see them. But then we're back to modal logic, and there we disagree. — Amalac
If we could see them, then eventually (if space has some ultimate limit, even if we could never see it) we would have to reach something that is not transparent and not translucent by logical necessity. — Amalac
I'll answer a few of your other points later, right now I've some work to do. — Amalac
I wonder if physics allows for anything that's totally transparent to all energy. — fishfry
I have no idea but that "anything" would be impossible to detect as detection requires some form of interaction but transparency means none of that. Good day. — TheMadFool
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