@ZaneScheepers Either a percept, if you don't care to distinguish it from a percept as a result of perception; or a hallucination, if you do

There's also always the "middle-ground" word illusion

@HWalters ok, so just to make sure we're on the same page, is 'visible light' is a distal stimulus?

Some philosophy inspired by the concept of infinity:

(cognitive) bias can make something invisible, unreachable etc. without the person knowing. It is like as if they are walking along a never-ending path without being aware of it and never reach the goal no matter how hard they tried

Sometimes, for some problems where the possible solutions are of a manageable number, brute forcing can sometimes help get the answer, since such mechanical approach will bypass bias mostly

It might be interesting to identify all metaphysical concepts that has a similar property as bias above, in that they can silently make something unachievable. This might help in identifying unique solutions to some problems, source of errors in experiments and also risk factors in safety workplace

The above in inspired when I did a safety induction test, I can never get the correct answer until I brute force it, which lead me to a bewilderment. It is possible some cognitive bias prevent me from seeing the correct steps need to take to handle the emergency in question

One possibility of that cognitive bias is my tendency to deal with the incident first, instead of other people's safety first when an emergency happens

Sometimes for challenging scenarios like this, being able to get the answer is halfway towards the solution, and then one need to force oneself (more accurately, one's own bias) to understand why the answer is such in order to have hopes of minimising it in the future

(Cognitive) bias! Is that a fancy word for preconceptions?

If it is, I can confirm that they do influence how we see things. We mentally manipulate evidence to match our beliefs. Brain patterns are strengthened by constant use. It actually affects 'how we think'. An 8 year old has fewer preconceptions and is therefore more logical in their deductions.

It has something to do with 'brain plasticity' I think.

Well, cognitive bias exists often because our brain is taking shortcuts in order to address certain issues with the quickest response possible. It can help only in said specific context

It is related to preconception, but I suspect congnitive bias is broader since it does not just include quick judgement that is consciously made due to a certain opinion on the given incomplete information, and involves everything that the brain uses t take shortcut in order to process limited information in a short time

"Put on hold as unclear what I'm asking"! physics.stackexchange.com/q/384045/179467

Seriously? Unclear to who?

Incomprehensible to many, yes. That I'll accept. youtu.be/kSuVJm4TI5c

The visible spectrum is so called because it is the range of wavelengths that we can see

Biologically speaking, we infer the existence of some object often by the light that bounce off it which carry the information

So in physical terms, we see the information of the light due to its interaction with the object, and after being processed by our brains, we then infer the existence of the object

You have it backwards. We infer light because we perceive the mind model of objects.

Air is not visible. If air was visible we would be blinded by a thick fog. Likewise, light is invisible, if light was visible, we would be blinded by a 'thick multi-coloured fog'

Another example of (cognitive) bias, affecting logical deduction

Ok, first step in talking about philosophy: I need to know exactly what you meant by "visible"

Consciously perceivable

Cats, trees and people are visible objects

right, now take a step back. biologically speaking, there are two ways where an object will become consciously perceivable

You mean the process?

yup

Detecting light is part of the process

By which 'objects' are made visible

yup, so for the 1st route, light has to hit our retina, which is then transformed into electrical signals which is then interpreted by the brain to reconstruct the object and hence we have the conscious perception of the object

Yup

As for the 2nd route, our brain, in the process on trying to process the sensory information from the external environment, sometimes will go into memories and past experience. This generates an internal feedback, which if the neurones involved are those related to the optical region of the brain, will cause us to have an illusory but conscious perception of an object

Yup

It is considered illusory because the signals that responsible for that perception is not due to external stimulus such as light entering our eyes

and I suspect, when you said about perceiving the mind model of object, you might be referring to this second mechanism

Actually, it plays a part in normal vision too. As the strawberry illusion illustrates

No. I'm specifically referring to the first. Perception based on light detection

Re 1st line: indeed, it can shape how the external data is processed, this is simply the way how brain take shortcuts. Instead of computing everything, it anticipates what it is going to see

Re 2nd line: In that case, I think I need to know what you meant by a "mind model" (which I am not sure if there is an analogous term in cognitive science)

Representational reality. Indirect realism.

We don't perceive reality outside us directly. We perceive our brains representation of that reality.

It includes a representation of us.

Yes

Consider the following experiment: You pick up a remote control, position it some cm away from your eyes, and then you click the remote. Do you see anything?

Within this representational reality there are representation of objects.

Yes. I see the diode glowing red.

I see the source

Brightness is a sensation, resulting from over stimulation of our light receptors.

Brightness can 'blind' us from seeing the source, but light itself is not bright.

yes and no

Explain

This is because the sensation of brightness is by the brain interpreting a large amount of electrical signals from the retina neuons. In principle, you can attach electrodes to these regions, and apply an electrical current, this will stimulate those neurones and you will also have a sensation of brightness even if there is no light

Meanwhile, light itself when it hits the retina, it can also trigger electrical signals on the retina, which our brain interpret as brightness

Proving that brightness is a percept

so in theory, one can go blind if their retina get over stimulated

Yup. But not because we see light

We can prove that light can contribute to the sensation of brightness given we understood brightness is the electrical signal from the neurons interpreted by the brain

Take a piece of live retina section which is connected to an ammeter, shine some light onto it, you will see the needle of the ammeter deflect

Therefore light is perceived as bright because it stimulate our neurons to give the electrical signals

Yup

Our light receptors detect light. I fully agree

Scroll down to the definition of physicsclassroom.com/class/light/Lesson-2/…

sounds right

The 'visible light spectrum' is not the light we see. It's the light which makes objects visible. Agree or disagree, it's a question worth asking. Definitely not "Unclear as to what you are asking!".

Well, have a look at this which explains (in the above neural language) on why IR and UV are not visible, even though it can be "see" by us in the sense that it enters our eyes:

and you will notice why the two notion of visibility coincide

Tldr: version: IR is not energtic enough to excite the electrons to give the electrical signals that give rise to the perception of brightness, hence to our brain, it is as if it is not there

whereas for UV, the energy is too high it breaks down our light receptors, hence also no signal corresponds to the sensation of brightness is sent

And therefore our brain doesn't create any images

exactly, hence the object looks invisible by these wavelengths

So technically speaking, all parts of the electromagnetic spectrum fall onto our retina, but only that narrow section called visible have the correct energy to trigger the electric signals which give rise to the sensation of brightness and the image of the object

Now you understand.

Wasn't too difficult was it?

Why can't others get it?

Well, I just happened to have strong interests in both philosophy and science to have the background to translate the language of both worlds. As you can see up there, we need to be careful and precise on the process involved in the creation of a conscious process (the input, the process and the output). All of this is then translated to the corresponding science language, and then the science people will understand

This is why in a physics perspective, the question as in its current state was classified as unclear what you are asking

(Of course, the other reason is that it is quite irrelevant to the physics since the two notions of visible makes no difference, and hence does not affect the interpretation of the phsyics theory, as that feymann lecture hinted)

But that's stupid. How can light be visible in physics and invisible in neurology and philosophy?

because to physicists and biologists, "visible" is defined by whether when the light hit the light receptors, it can generate the image of the object via the electrical signals produced

whereas in philosophy, "visible" I think involves a much broader notion that includes the formation of the image and why

(also note on terminology: "neurology" is a study of neuro and brain diseases, "neuroscience" is the term you use. "cognitive science" is a subfield that address about how our brain perceive things)

Thanks

So it's neuroscience and philosophy

@ZaneScheepers Typically, no, light is not a distal stimulus. But it can be.

If I have a cup in front of me, and I'm looking at that cup, the cup is the distal stimulus.

If there's a slightly smoky room, that's a bit dark, and someone shines a visible laser light through it, and I look at its path, then in that case the light is the distal stimulus

The light, or the illuminated dust in its path?

The light

Without dust you wouldn't see anything.

Yes, but your percept is a representation of the light

Not strictly of the "photons", but of a pseudo-object forming a straight line

No. It's a percept of dust

Simplistic, but effective.

Uhm, sorry, but no. It's no more a percept of dust than your mental image of the cup you're looking at is a percept of molecules

Illuminated dust in contrast to unilluminated dust.

Irrelevant anyway. You admit it's not photons we see.

But you don't see the dust

Photons are light. Brightness is a percept

In the sense that, the fact that there's dust there being illuminated is something you might know about, but it's not something you perceive to be there in this case

The same can be said about light

I think the term used is size-less!

You're perceiving a pseudo-object that is a straight line

You could quibble and call this a "laser path"

A representation of light?

It doesn't quite matter... such quibbling would be fair game...

...but you're looking at pseudo-objects right now as you're reading this

The pseudo object that is the laser path, is really a collective reflection of light from a row of dust particles in its way

So however we wish to quibble, we should do so, because pseudo-objects are quite popular in the modern era

so ultimately, it is the dust that is the distal stimulus

Secret: The problem is, when I look at a cup, I don't see the molecules

I have no percept of the molecules there

We cannot see the actual details of such dust most of the time because of the brightness of the laser light

Sure, dust is bigger, but it's the same thing

So is the light the distal stimulus or the dust?

and also that it is too small for the light to resolve its details

In order to be able to see details, the object has to have at least the same length as the wavelength of the light being shined onto it

if the object's details have a smaller separation than that, then the wave like property of light will mean you cannot resolve the details

Because we see 'the object' reflecting the light.

Okay, so we should just say either that there's no distal stimulus, or that the distal stimulus is a pseudo-object; I suppose "illuminated dust" is okay, but strictly that's dust+light

A "rainbow" might be a more problematic pseudo-object to consider

Shapes rendered on screens slightly less problematic

Well, as for that, refer to the following diagram:

Technically a single drop of water is all you need to see a rainbow, but it will be too faint. When multple raindrops refract the light, it splits into colors and you see the raindbow.

It is indeed quite probelematic in terms of classification because the raindrop is transparent

so you could very well argue that the distal stimulus is actually the sun itself, split into multiple colors

Well, no... a single raindrop will not produce a bow

The other problem is, if I get my friend to look at the rainbow, and I point it out to him, he'll see it... but strictly, he's looking at "something else"

Any reasonable distance... even inches... results in a bow produced by entirely different sets of raindrops, in a slightly different virtual position

My disagreement with your diagram is that the drop is way too big and too close... make it a lot smaller, and put it a lot further away, and those angles between colors become huge

Anyhow, Zane, I think treatment of perception as going from the object to the brain and ending at a percept is apt, but it's really only part of the picture

There's a bigger process that happens, that shapes perception

For "ordinary" objects, we use those percepts to build world models, we use the world models to plan goal-based actions, and even when we instantiate the action to attain a goal, we invoke perception to help guide the behavior while attaining the goal

That process doesn't just go from world to mind; it goes from world to mind to world to mind to world and so on, forming a connected circle

Maybe for example I'm thirsty, and that cup has some refreshing beverage in it

I see that, so I pick the cup up and drink from it

There's a lot of stuff that's behind that simple act

Indeed, for the above concepts phrased in terms of cognitive science, our brain is constantly updating its internal image based on external stimulus

Another interesting pseudo object is shadow, as illustrate by this vsauce video

Anyway, pseudo-objects of that sort are interesting because there's still "something" there. But to help carve the definition out, this square has no distal stimulus.

This was what I was trying to get at with the dust earlier. "Distal stimulus" isn't merely a "thing" in the world that we're looking at... it's a thing corresponding to a percept. We can certainly look at a neon spread illusion, but it's not a distal stimulus unless there's an object corresponding to the percept.

ie dust.

The sky is blue, although air is invisible. On the moon, the sky is black. The sky we see is a percept