JeffreyAK

We can't really separate objective reality from our interpretation of it, since that's going on in our brains. Blue, for example, is a mental construct, the way we interpret light wavelengths around about 475 nm when that light is picked up on our retinas. Lots of people can't tell the difference between blue and green, so their conscious reality is different from other people's. And the sky would look dramatically different if our eyes were sensitive to ultraviolet or infra-red light. On a grander scale, space itself is deformed by mass in ways we can calculate but can't really comprehend, but our conscious reality is Euclidean 3-space. Even the mathematics we use to describe reality affects and limits our perception of it, since math is continuous but reality appears to be discrete or quantized. Complicated stuff.

andyh

it corresponds to the range of wavelengths of visible light that we call "blue", so yes, the sky is "blue". whether you perceive that light as "blue" in the same way as I do is impossible to tell. for all we know, you might perceive "blue" in the same way that someone with synesthesia perceives middle C or ham sandwiches.

in any case, we are extremely limited in what we *can* perceive (directly). we can only "see" a tiny segment of the electromagnetic spectrum & are similarly restricted in our other senses. the world would be objectively the same if we saw in infra-red & had a bloodhound's olfactory sense, but we'd perceive it very differently.

AlericB

I agree with what you say about the correspondence between the wavelength of visible light and what we perceive as colour, and also with your point that only you can say how you perceive "blue". But isn't this saying that "blue" is this perception and not an actual property of the sky?

"Blue" is not even a property of the range of wavelengths. It is how our brains interpret these wavelengths.

andyh

"blue" is what we agree to call what most people seem to perceive similarly. we seem to be going off on a bit of an epistemological tangent here ... what was the question again?

AlericB

I think it was whether things that matter to us exist or not.

Carlotta

It is kind of fascinating that we can agree that the sky is blue but what I see might be different from what you guys see.
Blue to me might actually not be blue to you (according to your perception) yet we agree to call it the same.

AlericB

Yes, you are directly aware of what blue is to you but I can only know this indirectly and partially from what you tell me. For example, you might say that blue is a relaxing and retreating colour and this may give me some idea of what it is like for you.

I don't think that this is all just meaningless philosophy so I hope it's not off-topic. It illustrates that we have our own subjectivity and also that this subjectivity is not isolated and cut off from everything else. We each see blue in our own way and in a way that only we can really know but we also need real things in the real world such as the sky in order to have this experience. So the general point is that we all have an awareness of the world but we each form our own perspective on that world.

dwtbd

I think our senses are valid, that what we perceptually experience via the senses is a ‘true’ representation or picture of the ‘world’ as it is, we see a blue sky because the sky is blue.

By what logical means can you postulate that the world is other than how we apprehend it perceptually?

Optical illusions are usually brought up to buttress the idea that we can not trust our senses. Take the image of stick partially submerged in water, it appears bent but it actually remains straight , proof they say that the senses can’t give us a ‘true’ picture. But what we are seeing is the effect of distortion in the interplay between light and water and even if we don’t know or can’t understand how the phenomenon works, our eyes can’t help but ‘show us the truth’.

JeffreyAK

Here's a good example,


The camera angle on the right is different, right? The lines in the pavement diverge from some point on the lower left?

Nope, the two pictures are absolutely identical. The reason most people think they're not identical isn't because of our senses, per se, it's because of how our brains interpret what we sense. We can't separate the two, because what we see is what our eyes collect that is processed by our brains.

The "big moon illusion" is another good example. Nearly everyone is convinced that a low full moon near the horizon is much larger than full moon high in the sky, it's a common human experience that has generated much poetry and many lyrics to songs. But it's not larger, instruments prove that. We still don't really understand why our perceptions are wrong.

AlericB

As well as with his optical illusion post, JeffreyAK gave a good example of this earlier:

We see matter as something solid located in three-dimensional space but physics tells us that it is not like that it all and talks about, for example, electrons as being probability-waves in 11-dimensional Hilbert space only collapsing into particles under specific conditions of measurement. And even then, only the probability of finding them at a specific location can be predicted according to Heisenberg's uncertainty principle which says that particles can't be assigned both a determinate position and momentum at the same time.

Whatever all this means, the world has a deep and complex mathematical structure and is nothing like the world we see and touch and feel. It is certainly not made of matter in the sense of solid bits of stuff, precisely located in 3-dimensional space.

Another example would be that we see each other as solid bodies however the reality is that we are made up of atoms with swirling electrons. Our perception, the way that things appear to us, is clearly not an accurate guide of the way things really are.

andyh

when we see, we're always comparing what we see to what we've seen before & trying to recognize each thing as a shortcut to our existing understanding of that class of thing. this means that we usually don't take in all the details of everything we see, rather just enough to recognize the thing & move on to the next thing. young children are seeing things that are totally new to them all the time, but as adults it's rare that we see anything for which we have no existing reference.

as in the video, if we're on the look-out for something of interest, or a threat, then we can very easily discard much of what we're seeing to concentrate on some particular thing.

the stick in the water appearing bent is interesting because we do interpret the light hitting our eye correctly, we're not mis-interpreting what we're seeing as we are in a perspective illusion. if we can see that the stick is half-in & half-out of some water then we might take this into account & doubt the literal interpretation of what we're seeing.

dwtbd

There are categories of difference in our understanding of 'things' ,yes? Eg What?, How ?,and (deity notwithstanding forbid) Why?

Scientific knowledge and its ruthlessly and relentlessly logical language of the 'maths' give us the How answers. But the starting point has to be philosophic , no ? We first have to identify the What before we can apprehend the How it works.

The question I was commenting on , the validity of the senses , is basically the same debate western philo has been having since Plato and Aristotle , no ?

I'm way more Aristotelian when I stub my toe

AlericB

But we can't identify something like an electron or 11-D space through either our senses or philosophy. We need physics for that.

So I think philosophy comes in more towards the end as an attempt to understand as far as we can what things are in themselves. As with the blue sky example, things as they are in themselves are largely 'hidden' and do not correspond neatly to things as we apprehend them whether in perception or in maths. or in some combination of both.

dwtbd

I tend to see philo as the base and the knowledge of physics as an outcome of the interplay between our capacity for rationality and our apprehension of what is.

The maths told us to look for the Higgs boson and the LHC showed us the squiggly lines, no ?

But I'm willing to agree to disagree

AlericB

And that's exactly my point: the LHC can only show us squiggly lines, not the Higgs boson. What the Higgs boson is in itself behind the veil of analytical measurement and mathematical modelling is, I think, where philosophy comes in.

Me too. I'm not certain about anything!

JeffreyAK

An important philosophical point, this isn't a Higgs boson, it's a bump on a graph of analyzed data, deduced by detection of other secondary decay objects that show up in raw data we wouldn't be able to interpret unless we were working in the field,


Human brains provide the direction for setting up the experiment and interpreting the little bump as strong evidence that the Higgs boson does exist with a particular mass, but we still don't know what a Higgs boson is. Is it a particle? Yes. A wave? Yes. A quantum excitation of the Higgs field? Yes, but we don't really know what that means except through mathematical equations.

So our understanding of the Higgs boson is divorced from our senses, and we have to feel around in the dark for it, using math-based physics. General relativity is even stranger, and further divorced from our senses because it contradicts those senses (linear time independent of space, Cartesian coordinates, etc.)

AlericB

Yes, the maths. is describing some aspect of the physical world but we can never be sure exactly what it is. The quantum theorist Bernard d'Espagnat calls it a 'veiled reality' since we can't know exactly what concepts like the Higgs boson or measurements like the bump in your graph correspond to, if correspondence is even an appropriate term any more.

dwtbd

Back to the validity of the senses as the implicit base of all knowledge, why did you show us a graph?

JeffreyAK

Well I think it demonstrates, we don't sense a Higgs boson, and in fact we can't really comprehend what it is. We sense indirect evidence (a bump on a graph we can look at with our eyes, yes, I think I see your point) for the existence of a Higgs boson, after we use our brains to design an experiment, count hits on a detector we used our brains to make, and then view a graph we used our brains to put together based on those hit counts, all rooted in a theory our brains came up with that postulates the existence of a Higgs field. Lotta links there, and breaking any one of them could tank the whole interpretation, so we're on much shakier ground than if we were all to stand in a room surrounding a rock and try to agree if there is, in fact, a rock in the middle of the room.

dwtbd

Agreed , lots and lots of links each very important to getting it right.