I stated that without the concept or idea of what a tree is, there is/may be no tree. — Cavacava

Okay, but then what happens when you decide to run through the unconceptualized blob of green & brown? — Marchesk

Without concepts, you cannot make predictions. You can only live in the moment. Roughly speaking, to conceptualize the visible (i.e. what you have experienced) is to imagine the invisible (i.e. what you did not experience.)

When you look at that duck-rabbit picture, your brain cannot decide, solely on the content of that picture, whether the animal is a rabbit or a duck. It can decide that it is an animal but it cannot decide what kind of animal. This is because that particular view is ambiguous.

Note that an animal is more than just a single view of it. An animal is, properly speaking, an animation, i.e. a sequence of views, that is interactive. The duck-rabbit picture only shows one side of the animal.

. As I see it, only philosophers ever bother with the issue in the first place. — t0m

That's like saying only mathematicians bother with questions like Fermat's last theorem.

Except that questions about whether we really perceive the real world do crop up among average people, and make it into literature and the media. You have people like Elon Musk claiming we're in a simulation and asking scientists to find a way out, or whatever.

Philosophy is like art, math and sport. They are activities humans engage in, but anyone can find those activities to be pointless, or meaningful.

But they're not. One is talking about a simulation running inside your head by which you're indirectly aware of an external world.

The other is talking about there being no simulation, just direct access to the external world. — Marchesk

And what do you mean by direct access to the external world? Presumably you're not saying that my experiences are the tree, because that would be subjective idealism. Presumably you accept that my experiences (i.e. sense-data/qualia) are one thing and the tree is something else. So what does it mean for sense-data/qualia to provide "direct" (or for that matter "indirect") access to the tree?

Both the direct and the indirect realist will likely argue that the nature of our experiences (the particular quality of the sense-data/qualia) is causally covariant with the nature of the tree (being that the tree is causally responsible for the experience), but beyond that, what's the difference between saying that the experience is direct or "just" a simulation?

So what does it mean for sense-data/qualia to provide "direct" (or for that matter "indirect") access to the tree? — Michael

Direct realists deny that there are sense-data. Your access to the tree is direct because you're not aware of some idea in the mind (sense-data), you're aware of the tree.

but beyond that, what's the difference between saying that the experience is direct or "just" a simulation? — Michael

The difference is what we're directly aware of when having a perception. The indirect realist has to make an inference to an external tree. The direct realist does not.

Direct realists deny that there are sense-data. — Marchesk

So are you saying that the image of a tree is the tree, or that there's no such thing as the image of a tree?

And what are dreams/hallucinations if not the occurrence of sense-data?

The difference is what we're directly aware of when having a perception. — Marchesk

Repeating the claim "awareness is direct" doesn't explain what it means for awareness to be direct.

As long as 'perception' continues to be spoken about as a 'mental', imagistic phenomenon - and not the bodily/physinomic, interactive, environmental, affective, anticipatory, and memory-laden process that it is - this thread will continue to be mired in aporia - as it currently is.

And what are dreams/hallucinations if not the occurrence of sense-data? — Michael

Agreed, and it's a problem for direct realism, far as I'm concerned. Disjunctivism is one way of dealing with that.

So are you saying that the image of a tree is the tree, or that there's no such thing as the image of a tree? — Michael

No, image of the tree is seeing the tree.

Repeating the claim "awareness is direct" doesn't explain what it means for awareness to be direct. — Michael

You perceive a mind-independent object, not a mental image, sound, etc.

Reasoning is by its nature indirect. The purpose of reasoning is to make guesses regarding something that is unknown (i.e. something that hasn't been experienced or at the very least something that hasn't been memorized.) Thus, to say that knowledge acquired through reasoning is direct is false. Only what has been experienced in the past can be said to be direct. And how do we call these things that have been experienced in the past if not phenomena, sense-data, qualia, events, neutral stuff, etc?

As long as 'perception' continues to be spoken about as a 'mental', imagistic phenomenon - and not the bodily/physinomic, interactive, environmental, affective, anticipatory, and memory-laden process that it is - this thread will continue to be mired in aporia - as it currently is. — StreetlightX

I'm not sure how putting it in those terms dissolves the philosophical issue of what a perceived tree is, or the skeptical concern that we can't know. Also, we do experience mental* images, and when we see a tree, it can be similar in experience to having a hallucination or dream of a tree.

* Or image generated by our nervous system (or bodily organism), if you prefer. Meaning, it's not external to our being, and thus publically shared.

You perceive a mind-independent object, not a mental image, sound, etc. — Marchesk

I'm asking for the distinction between perceiving a mind-independent object and perceiving a mental image. I don't get it. Both the direct and the indirect realist will argue that (waking) experiences are caused by external stimulation, but then the former wants to say that the perception is of the external stimulation and the latter wants to say that the perception is of the experience. Except for the wording, I don't understand the difference.

No, image of the tree is seeing the tree.

Remember the infamous dress? Everybody was seeing the same picture, but some saw it to be black and blue and some saw it to be white and gold. So despite the fact that there was a shared object of perception, the image differed.

Remember the infamous dress? Everybody was seeing the same picture, but some saw it to be black and blue and some saw it to be white and gold. So despite the fact that there was a shared object of perception, the image differed. — Michael

But then, if the image differed, was there a shared object of perception? Some were aware of a black and blue dress and some were aware of a white and gold dress.

As I said before, it's just different ways to talk about the same thing. You can say you're aware of the image (a white and gold dress for some, a black and blue dress for others) or you can say that you're aware of the external stimulation (the photo).

I'm not sure how putting it in those terms dissolves the philosophical issue of what a perceived tree is, or the skeptical concern that we can't know. — Marchesk

It dissolves it because it puts to ground the untenable, philosophically atrophied distinction between the 'mental' and the 'thing itself'; the very question posed by the OP is an error. The challenge is not to answer it but to reformulate its terms entirely.

I'm asking for the distinction between perceiving a mind-independent object and perceiving a mental image. I don't get it. — Michael

When you dream, hallucinate, visualize or remember a tree, it's only available to you. When you perceive a tree, other people can also perceive it. Realists say this is so because the tree is mind-independent.

but then the former wants to say that the perception is of the external stimulation and the latter wants to say that the perception is of the experience. Except for the wording, I don't understand the difference. — Michael

It's whether the content of perception is the same as dreaming, hallucinating, etc. or not. What causes it is another matter.

If the indirect realist is correct, then we're seeing the equivalent of a dream tree, like when Morpheus tells Neo he's been living in a dream world. The only difference being that there's an external cause for the perception, which may be similar to the tree, or something entirely else, such as the noumena.

But if the direct realist is right, then what we see is what we get, within the limitations of our sensory organs (obviously science is still needed here).

It dissolves it because it puts to ground the untenable, philosophically atrophied distinction between the 'mental' and the 'thing itself'; the very question posed by the OP is an error. The challenge is not to answer it but to reformulate its terms entirely. — StreetlightX

I understand, but I don't see how it accomplishes that, since we do have sensory experiences which are not externally generated.

But if the direct realist is right, then what we see is what we get, — Marchesk

So direct realism is as described in the Wikipedia article (even though so many have taken issue with it when I bring it up):

• There exists a world of material objects.
• Some statements about these objects can be known to be true through sense-experience.
• These objects exist not only when they are being perceived but also when they are not perceived. The objects of perception are largely perception-independent.
• These objects are also able to retain properties of the types we perceive them as having, even when they are not being perceived. Their properties are perception-independent.
• By means of our senses, we perceive the world directly, and pretty much as it is. In the main, our claims to have knowledge of it are justified.

The fourth point is where I think direct realism fails. The properties of the experience (colour, smell, taste, texture, shape) are properties of the experience and not properties of the external-world stimulus. The properties of the external-world stimulus are causally covariant with the properties of the experience, but they are not the same. For example, a sweet taste is causally covariant with the apple's chemical structure, but isn't a property of the apple, and a red colour is causally covariant with the apple's surface (and/or the reflected light), but isn't a property of the apple's surface (and/or the reflected light).

When you dream, hallucinate, visualize or remember a tree, it's only available to you. When you perceive a tree, other people can also perceive it. Realists say this is so because the tree is mind-independent. — Marchesk

Each one of us has his own experiences. When we say that we both perceive something (e.g. that the sky is blue) what we mean is that we have similar experiences. Nothing else.

Each one of us has his own experiences. When we say that we both perceive something (i.e. that the sky is blue) what we mean is that we have similar experiences. Nothing else. — Magnus Anderson

What we mean is that we have similar color experiences when looking at the same sky.

When we say that we both perceive something (i.e. that the sky is blue) what we mean is that we have similar experiences. Nothing else. — Magnus Anderson

Well, I would add to this that we also mean that the same external stimulus is causally responsible for the experience.

The fourth point is where I think direct realism fails. The properties of the experience (colour, smell, taste, texture, shape) are properties of the experience and not properties of the external-world stimulus. The properties of the external-world stimulus are causally covariant with the properties of the experience, but they are not the same. For example, a sweet taste is causally covariant with the apple's chemical structure, but isn't a property of the apple, and a red colour is causally covariant with the apple's surface (and/or the reflected light), but isn't a property of the apple's surface (and/or the reflected light). — Michael

I would agree with that. But are there some properties that we do directly perceive, such as shape?

The word "external" means "outside of (some set)". Similarly, the word "internal" means "within (some set)". The set (or more accurately, category) always refers to some range of experience. There is thus no dichotomy between experience and reality that is separate from our experience. There is only dichotomy, or rather polychotomy, between different kinds (or classes, or categories, or sets) of experience. This view is very close to that of Ernst Mach and William James that is known as Neutral Monism.

But are there some properties that we do directly perceive, such as shape? — Marchesk

I don't think so. As studies have shown, there's no a priori connection between shapes-as-seen and shapes-as-felt. Those born blind who later gain sight aren't immediately able to determine the shape of an object just by looking at it. It takes time to learn the shape of an object by sight. So given that a circle-as-seen and a circle-as-felt are very different, what is "objective" circle-ness like? A circle-as-seen or a circle-as-felt? I don't think it's "like" either. A visual circle is just an experiential effect of the right kind of external stimulation, just as a tactile circle is just an experiential effect of the right kind of external stimulation. I think it very wrong to think that things look (or feel) like something even when not being seen (or felt).

A visual circle is just an experiential effect of the right kind of external stimulation, just as a tactile circle is just an experiential effect of the right kind of external stimulation. I think it very wrong to think that things look (or feel) like something even when not being seen (or felt). — Michael

But objects do have shapes, and those shapes are important to how the objects interact with the world. When we see a circle, we see that shape because the light bounces off it that way. When we feel the shape, we can tell that it's rounded, and if a blind person walked around a shape, they would know they went in a circle.

The set (or more accurately, category) always refers to some range of experience. There is thus no dichotomy between experience and reality that is separate from our experience. — Magnus Anderson

Science claims otherwise. There is big universe that exists beyond and before, and after us. But our everyday experiences tell us the same thing. The big oak tree has 120 rings. It was alive before I was born, etc. And all of us were born, before we experienced anything. This goes all the way back before humans, and eventually, before life and any sort of experience.

What we mean is that we have similar color experiences when looking at the same sky. — Marchesk

It applies to any kind of experience. When two men look at a wheel and agree that its shape is circular what that means is that their "shape" experience is similar.

I understand, but I don't see how it accomplishes that, since we do have sensory experiences which are not externally generated. — Marchesk

Those 'sensory experiences' are precisely what happens when the the vast physiological and psychological machinery that regulates our perception are not constrained by environmental affordances: dreams and hallucinations are the ultimate proof that there is a shit-ton that is 'contributed' by us in the process of perception, and which is let to 'run free' in abnormal circumstances. Another way to put this is that the difference between waking and dreaming is vastly overstated. Here is Evan Thompson on dreams:

"Wakefulness is nothing other than a dreamlike state constrained by external sensory inputs... the brain sustains the same core state of consciousness during REM sleep and wakefulness, but the sensory and motor systems we use to perceive and act can’t affect this consciousness in regular ways when we’re REM-sleep dreaming. Consciousness itself doesn’t arise from sensory inputs; it’s generated within the brain by an ongoing dialogue between the cortex and the thalamus. The difference between wakefulness and REM sleep lies in the degree to which sensory and motor information can influence this thalamocortical conversation. During REM sleep, sensory inputs are kept from entering the dialogue, while motor systems are shut down (you’re paralyzed except for eye movements) and attention fastens onto memories.

Simply put, when sensory inputs participate in the thalamocortical dialogue generating consciousness, they constrain what we experience and we have waking perception. When sensory inputs can’t participate in this dialogue in sleep, we dream. To put the idea another way, from the brain’s perspective—or rather from the perspective of the thalamocortical system sustaining consciousness—wakefulness is a case of dreaming with sensorimotor constraints, and dreaming is a case of perceiving without sensorimotor constraints." (Thompson, Waking, Dreaming, Being - this book has so much else to say on this subject, you really ought to read it).

This being a more scientifically elaborated idea which Bergson had decades ago: "We must suppose, in deep sleep, at least a functional break in the relation established in the nervous system between stimulation and motor reaction. So dreams would always be the state of a mind of which the attention was not fixed by the sensori-motor equilibrium of the body. ... If our analyses are correct, the concrete feeling that we have of present reality consists, in fact, of our consciousness of the actual movements whereby our organism is naturally responding to stimulation; so that where the connecting links between sensations and movements are slackened or tangled, the sense of the real grows weaker, or disappears." (Bergson, Matter and Memory).

Perception is loop that runs from body to world and back again; when the loop is broken or interrupted, there is still alot that goes on, but it does so aberrantly, in fragments. Hence the weird phenomenology of dreams, the general tendency to 'float' (unconstrained by a fixed body!), the general fragmentary nature of dreams, etc.

When two men look at a wheel and agree that its shape is circular what that means is that their "shape" experience is similar. — Magnus Anderson

What it means is that there is a circular object that gives rise to the experience of seeing a circular shape, and that's why two people can have similar experiences. Also that's why there are two people.

But objects do have shapes, and those shapes are important to how the objects interact with the world. When we see a circle, we see that shape because the light bounces off it that way. When we feel the shape, we can tell that it's rounded, and if a blind person walked around a shape, they would know they went in a circle. — Marchesk

They might have a shape, but that shape isn't anything like a shape as seen or as felt. I think you're committing the same error of conflation that some do when they talk about things having a colour. Red-as-seen isn't anything "like" light with a wavelength of ~625–740 nm (or a surface that reflects light at this wavelength). Sweetness-as-tasted isn't anything "like" the chemical composition of sugar.

Things don't look or feel like anything when not being seen or felt. It's naïve (realism) to suggest otherwise.

Science claims otherwise. There is big universe that exists beyond and before, and after us. But our everyday experiences tell us the same thing. The big oak tree has 120 rings. It was alive before I was born, etc. — Marchesk

The problem is that people confuse actual experience (i.e. sense-data that we possess) with potential experience (i.e. sense-data that we expect.) Even though I was born long after Alexander the Great died, I do not deny the potential experience of seeing him in person.

Very interesting, thanks. That would seem to largely support indirect realism, even if you're not interested in framing it that way. It also seems to support the Cyrenaic view of perception, which was that it was the result of bodily movements, with the addition of external inputs.

It doesn't really help alleviate skeptical concerns, or tell us much about the nature of the external inputs. As Michael points out, the external inputs can be totally unlike what consciousness presents us.

Things don't look or feel like anything when not being seen or felt. It's naïve (realism) to suggest otherwise. — Michael

So we're left with mathematical abstractions?