Realismi

Skepticism and the Veil of Perception – Michael Huemer

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Introduction: The Problem of Perceptual Knowledge

Hold a finger in front of your face. Focus your eyes on the finger, but attend to a distant object in the background. If you’re doing this right, the background object should appear double and blurry. If you now bring the background object into focus, you will see the finger in your visual field split into two, blurry fingers. There is, of course, a scientific explanation for why this happens. It has to do with the fact that each of your eyes has a different vantage point on the room; one of the finger-images is produced by your left eye, and the other by your right eye. But the scientific explanation is not our concern here.

Note:ESPERIMENTO

the relationship between perception and reality. Obviously, there are not really two fingers in the physical world. Nevertheless, you are “seeing” two of something. Therefore, we ask: What is it that there are two of?

Note:IL PROBLEMA FILOSOFICO

A number of philosophers have put forward the following answer: There are two images of the finger in your mind. It is these images—rather than the actual, physical finger—that you are directly aware of; that is why there appear to be two fingers.

Note:OGGETTO E IMMAGINE MENTALE

if the blurry “fingers” that you see are really only images in the mind, it seems that the in-focus “finger” is also an image in the mind.

Note:TUTTO È IMMAGINE

There are similar arguments for the rest of the five senses, to show that what we directly perceive is always an image or “representation” in our minds.

Note:VALE PER TUTTI I SENSI

All of this is leading up to the question: How do you know that you aren’t, right now, a brain in a vat?

Note:CERVELLI IN UN VASCA

Direct realists maintain—contrary to the argument given above—that we are directly aware of real, physical objects in perception and that this explains how we know about the nature of those objects.

Note:REALISMO DIRETTO

Indirect realists hold, instead, that our awareness of the real world is indirect. They accept arguments like the one given above, which says that what we are immediately aware of in perception is only mental images; however, they say that we can infer the existence of real objects corresponding to our images, because that is the best explanation for why we have the sort of mental images we do.

Note:REALISMO INDIRETTO

Idealists hold that there is no objective world; there is only the mind and the images, thoughts, feelings, and so on in the mind. (This is called “idealism” because the mental images used to be called “ideas.”)

Note:IDEALISMO

Skeptics hold that we cannot know that there is an objective world nor, if there is one, what it is like.

Note:SCETTICISMO

In the subsequent chapters, I will defend direct realism against all comers.

Note:TESI

When a person first hears about the brain-in-a-vat scenario, he is apt to have one of three reactions. Reaction #1: “That’s stupid. I refuse to talk about that.” Reaction #2: “Gosh, maybe I am a brain in a vat. How would I know?” Reaction #3: “What is wrong with this argument? And what can I learn from that about the nature of knowledge?” I would like to encourage you to cultivate reaction #3.

Note:REAZIONE ALLO SCETTICISMO

Objections to Direct Realism

I have just defended two traditional “direct realist” theses: first, that in perception, the things of which we are directly aware are the real, physical objects, and second, that as a result of perception, we know noninferentially that there are external objects having certain observable properties. I think this is the view of common sense, on both counts.

Note:DIFESA DEL SENSO COMUNE

I call it “direct realism,” but it is also often called “naive realism,”

Note:INGENUO?

Critiche al realismo diretto: The Argument from Perspective

But this universal and primary opinion of all men is soon destroyed by the slightest philosophy, which teaches us that nothing can ever be present to the mind but an image or perception…. The table which we see seems to diminish as we remove farther from it; but the real table, which exists independent of us, suffers no alteration; it was, therefore, nothing but its image which was present to the mind.

Note:CRITICA DI HUME

It is sometimes called “the argument from illusion,” but I beg leave to change its name, since the example to which Hume here appeals is an example of the phenomenon of perspective, not an example of an illusion.

Note:L’ILLUSINE

Now, says the indirect realist, since the character (specifically, the content) of our experiences depends on factors that have nothing to do with the character of the physical objects we’re supposedly (that is, according to direct realists) perceiving, we have to conclude that our experiences do not really count as awareness of those objects after all.

Note:CAMBIA LA PERCEZIONE MA NON L’OGGETTO

direct realists need not challenge the general premise about the nature of awareness. We can instead find properties of the external object that do vary alongside the variations in our experience to which the indirect realist is calling attention.

Note:IL COMPITO DEL REALISTA

What the sense of sight makes one aware of, directly and in the primary sense, is the angular sizes of objects, relative to the point at which the observer is located. Obviously, the angular size of an object will vary (assuming the object keeps the same linear size) depending on how far away from it one is. Given this, that the table will look smaller as you move away from it is precisely what we should expect if we are seeing the real table. This change marks no illusion; in fact, as Thomas Reid pointed out in his response to Hume, it is evidence in favor of our seeing the real object.

Note:LA VISIONE DELL’OGGETTO

it is essential to keep clearly in mind what is the issue between direct and indirect realists. The issue is whether the immediate objects of awareness in perception are subjective or objective—whether they are mental phenomena or physical phenomena. What I have done is to concede the relational character of these objects, but not their subjective character.

Note:L’OGGETTO DELLA CONTESA

In my view, then, the argument from perspective rests on a confounding of two distinctions: the objective versus subjective distinction and the intrinsic versus relational distinction. Perspectival variation shows that what we are directly, visually aware of is not an intrinsic property of the external object, since it depends on our position.

Note:CONFUSIONE COMUNE

Suppose you keep one hand in a bowl of ice-cold water for a minute, while at the same time the other hand is immersed in hot water. Then you simultaneously plunge both hands into a third container full of lukewarm water. What you would find is that the same water feels warm to the first hand and cool to the second hand. Traditionally, opponents of direct realism try to use this phenomenon to show that we do not really perceive the actual temperature of the water, for one and the same tub of water cannot simultaneously be both warm and cool.

Note:ACQUA CALDA

How should a direct realist explain what goes on in this experiment with the three tubs of water? One might try saying that you are aware of the temperature difference between the water and your hand. But there is a better answer: your sensations make you aware of the heat transfer between your hand and the water. The water “feels cool” to the one hand because heat is flowing from the hand to the water.

Note:SPIEGAZIONE REALISTA

Notice the strategy of this response: I concede that the property we are aware of in the example, the property we detect, is not an intrinsic property of the water (temperature). But nor is it something subjective (a sensation). Instead, I propose that it is objective but relational (heat transfer).

Note:LA STRATEGIA

I am not saying, here, that all the properties we detect through perception are relational; some of them, at least, are intrinsic. For instance, by the sense of touch, one can be aware of the ordinary, three-dimensional shapes of objects.

Note:NON TUTTO È RELAZIONALE

The Argument from Illusion

we make one more use of the optical illusion involving the stick half-submerged in water. The stick looks bent but is in fact straight. Can this phenomenon be used to show that we are not directly aware of the stick?

Note:LA RIFRAZIONE CHE CONFUTA IL REALISMO

The argument from illusion needs two stages. First, the indirect realist wants to argue that in this case, what one is immediately aware of cannot be the actual stick, and that it must be, instead, a sense datum. Second, the indirect realist wants to argue that if we are aware of a sense datum in this case, then we are also aware of sense data in normal cases, even when there is no illusion.

Note:L’ARGOMENTO DEL REALISTA INDIRETTO

I don’t think that, because the stick appears bent when it really is not, it follows that you are not directly aware of the stick. … Here is a logically sound argument: When you look at the stick, you are directly aware of something that is bent. No (relevant) physical object is bent at this time. Therefore, the thing you are directly aware of is something nonphysical. If (3) is true, then it would seem that we must posit a sense datum as being the thing that is bent.

Note:L’ARGOMENTO DEL REALISTA DIRETTO

first premise is false. When you look at the stick, you are directly aware of something (namely, the stick) that looks bent, but it is not in fact bent.

Note:ESSERE E SEMBRARE

When you look at the stick, you are directly aware of something that appears bent. No (relevant) physical object is bent at this time. Therefore, the thing you are directly aware of is something nonphysical.

Note:ARGOMENTO MODIFICATO DAL REALISTA DIRETTO

we could always say that we are aware of something that appears bent but isn’t.

Note:APPARENZA

My claims (a) that we are aware of objective, relational properties of physical objects in perception, (b) that in the case of illusions, we are also aware of physical objects, though they are not quite the way they appear, and (c) that hallucination is not awareness of anything,

Note:RIEPILOGO

The Argument from Hallucination

He asks us to compare a case in which a person sees a table with a case in which a person has a perfectly vivid and realistic hallucination of a table. Assume that the hallucination is qualitatively just like a perception,

Note:ESPERIMENTO RICHARD FUMERTON

The person with the hallucination has the same justification for believing there is a table as does the person who is seeing the table. In the case of the hallucination, the person’s justification for believing there is a table does not consist in his being directly acquainted with a table. Therefore, in the case of normal perception, the person’s justification for believing there is a table does not consist in his being directly acquainted with a table.

Note:ARGOMENTO FUMERTON CONTRO IL REALISMO DIRETTO

it is not an argument against my version of direct realism, because I do not say that our justification for believing in external objects consists in our being directly acquainted with them. I say that our justification for believing in external objects consists in the fact that, when we have perceptual experiences, external objects seem to us to be present, and there is no evidence in general against this. The person with the perfectly vivid hallucination also has an experience such that a table seems to him to be present and also (we assume) has no evidence against this; therefore, on my account, he has the same kind and degree of justification for believing in the table as we normally do when we see tables.

Note:NON CONFUTA IL REALISMO PRIMA FACIE

The Argument from Double Vision

If you look at your finger while it is out of focus, you will seem to see two fingers; alternately, you can induce double vision by pushing on one eyeball. Recall that the argument went, essentially, like this: In the case of double vision, you see two of something. There are not two (relevant) physical objects that you’re seeing. Therefore, what you see is something nonphysical.

Note:ARGOMENTO DOPPIA VISIONE

One possibility is to treat double vision as a kind of hallucination. We could then say: “You are not seeing two of something; you merely seem to be seeing two things.

Note:NON VEDO MA MI SEMBRA DI VEDERE

the correct description of the case is this: There is a single, physical object that you are seeing; however, that object seems to be in two places. That is, your visual experience incorrectly represents the finger in two different places.8 This is a case of a visual illusion.

Note:RICONDURRE ALL’ILLUSIONE

The Time-Gap Argument

Suppose you are looking at a star, up in the sky. Suppose the star is (or was) one thousand light-years away. That means that it takes 1000 years for light to travel from the star to where you are. Now, suppose that the star was actually destroyed 300 years ago. You would still be “seeing” it, because light it emitted before it was destroyed is still traveling towards Earth. People on Earth will continue to “see” this star for another 700 years. But wait—how can you be seeing something that doesn’t (now) exist?

Note:ESEMPIO DELLA STELLA

So what is it that you’re really seeing? Indirect realists have a ready answer, of course: a sense datum of a star.

Note:RISPOSTA INDIRETTA

Perhaps what you are really seeing is simply the light emitted by the star, rather than either the star itself or a sense datum. The light from the star continues to exist at the time you have the visual experience, so there’s no problem, right?

Note:LUCE

Here is another example. You’re in a large baseball stadium. You watch the batter hit the ball. A second after you see this, you hear the crack of the bat striking the ball, due to the fact that sound travels slower than light. Should we say that you are not really hearing the bat striking the ball, since that event no longer exists? Wouldn’t it be more natural to say simply that you hear the event a second after it happened?

Note:BASEBALL

The Causal Argument

It is well known that an object does not directly cause a perceptual experience in an observer—that there are intermediary processes that must take place in order for one to perceive a thing. In order for me to see the cup on the table, for instance, light rays have to travel the distance between the cup and my eye. Then electrical signals have to travel down my optic nerve. Then my brain has to process the information.

Note:INTERMEDIARI DELLA VISIONE

must we not conclude that I am not “directly aware” of the object?

Note:INTERMEDIARI=INDIRETTO?

if being directly aware of a thing means having awareness of it not based upon one’s awareness of anything else, then these considerations are irrelevant, for the aforementioned processes intervening between the cup and my experience of a cup do not include any states of awareness.

Note:NO

Brain processes cause my visual experience, but I am not seeing brain processes; I am seeing the cup.

Note:PROCESSI MENTALI

The Illusoriness of Secondary Qualities

According to this next objection, the physical objects around you are really colorless. The colors you think you are seeing on the surfaces of physical objects either do not exist, or exist only in the mind, as properties of sense data.

Note:I COLORI NON ESISTONO

It seems that any answer one gives to the question Which of the colors we seem to see under various lighting conditions is the true color of the object? will have to be merely stipulative.

Note:IL VERO COLORE

Put this another way: assume that color is really an objective property of the surfaces of physical objects. Then a physical object can have one and only one color (in a given place at a given time).

Note:UN OGGETTO=>UN COLORE

if we can never know the true color of anything, then why believe things have any true colors at all? Ockham’s razor would seem to dictate the elimination of such unknowable and explanatorily useless properties.

Note:RASOIO

Without even considering colorblind people, it is common to have two people disagree about the color of an object—for example, A says the shirt is red, B says it is orange.

Note:DALTONICI

If colors are really out there in the objects, this raises the question Whose color perceptions are right?

Note:CHI HA RAGIONE?

Third, we can make almost the same argument again by appealing to the more radical differences in color perception among species. Some animals can only perceive differences of light and dark, and not differences of hue.

Note:PERCEZIONE E SPECIE ANIMALI

Such are the arguments for the illusoriness of color. These arguments leave two alternatives open—if one accepts that physical objects aren’t colored, one might thence conclude that nothing has color, or one might conclude that colors are properties of sense data, rather than being properties of physical objects.

Note:O I COLORI NON ESISTONO O SONO NEI SENSE DATA

I believe that similar arguments can be given for tastes, smells, and sounds, to the effect that they are not in the objective, physical world either. Be that as it may, for the sake of brevity we focus only on colors.

Note:SUONI ODORI ECCETERA

let’s say that Bob has a pair of severely green-tinted glasses. When he puts on the glasses, everything looks green or black, regardless of what is (as we would ordinarily say) its true color. So now Bob has a red tomato in front of him. He puts on the glasses, and the tomato looks a very dark green or black. In this case, Bob is not seeing the color of the tomato,

Note:CAMBIO DI LENTI

There have been a number of philosophical theories about the nature of color, including: (a) There is no such thing as color. (b) Colors are properties of sense data. © Colors are dispositions that physical objects have to cause experiences of certain sorts in us. (d)Colors are dispositions that physical objects have to reflect light in certain ways. (e) Colors are complex properties of the surfaces of objects, including perhaps their textures and the electron structures of the molecules they contain, that explain the dispositions spoken of in (c) and (d). (f)Colors are undefinable and irreducible properties of the surfaces of physical objects. By calling them “irreducible” I mean they are not identical with any of the things spoken of in (c), (d), or (e), nor with anything else along those general lines.

Note:TEORIE DEL COLORE

All I need to do is show that (a) and (b) are not the most plausible alternatives. Alternatives (c), (d), and (e) all allow that physical objects are colored and so present no problem for direct realism as far as the present argument is concerned. It will suffice, then, to show that something along the lines of (c), (d), or (e) is more plausible than (a) or (b).

Note:INCOMPATIBILITÀ

I think (a) is implausible because it just seems obvious that I’m seeing a brown thing now.

Note:SENSO COMUNE

I propose to elaborate position (d), as perhaps the most natural and widely held sort of view.

Note:LA TEORIA PIÙ PLAUSIBILE

The main philosophical objection to such a view derives from the problem of metamers. Metamers are different spectral reflectance patterns that nevertheless look the same to the human eye … In other words, it is possible to have two surfaces that have very different spectral reflectance distributions, but that nevertheless look the same to us, so that we would classify them as the same color. …

Note:METAMERONE

we can say that there are two different systems for classifying colors. The scientific classification of spectral reflectance distributions (which are, in fact, colors) makes finer discriminations than the ordinary, everyday classification, but this does not make the latter wrong in an intrinsic sense; it simply answers to different interests.

Note:SISTEMI DI CLASSIFICAZIONE

We turn, now, to the first argument for the illusoriness of color: the apparent colors of things vary depending on the lighting conditions, so what are the conditions under which we perceive the true colors of objects? The obvious answer is: normal lighting conditions. That means reasonably (but not blindingly) bright, white light. So the pink look of objects under red light is just an illusion,

Note:NORMALITÀ

The vagueness of words in ordinary language provides an example of the same sort of indeterminacy; for example, there is no objective fact of the matter as to exactly how many seconds a person must have been alive in order for him to count as “old,” so the content of “old” is indeterminate.

Note:VAGHEZZA

The second argument for the illusoriness of color appealed to the variations in color experiences among normal humans, while the third appealed to the variations among species.

Note:DALTONICI E API

My response to these two arguments is the same. I say that these differences are differences in the qualia of the visual experiences, not in their contents. As a result, it need not be the case that one person, or one species, is “wrong.”

Note:QUALIA E CONTENUTO. L’INTERMEDIARIO NON INPLICA SENSE DATA

I have two major objections to indirect realism. One is epistemological: indirect realists make much easier targets for skeptics than direct realists do,

Note:IL REALISMO INDIRETTO FACILE PREDA DEGLI SCETTICI

The other major objection, which I will focus on in this chapter, is metaphysical. The indirect realist says that in perception, we are directly aware (only) of some sort of mental phenomena, which we’re calling “sense data.” The problem I want to raise for the indirect realist centers around the question Where are sense data located?

Note:OBIEZIONE AI SENSE DATA: DOVE SONO?

My argument against sense data, in brief, is this: In perception, the things I am directly aware of (at least sometimes) have locations. Only physical things have locations. Therefore, the things I am directly aware of in perception (at least sometimes) are physical things.

UNA LOCALIZZAZIONE DEVE ESISTERE

COMMENTO PERSONALE

La teoria difesa del realismo diretto resta poco convincente. E’ nella questione dei colori che appaiono tutte le sue debolezze. Per dire che i colori sono negli oggetti è costretta a ridurre il colore al suo spettro luminoso anche se a tutti noi è chiaro che quando diciamo “rosso” non ci riferiamo certo allo spettro luminoso di questo colore. Lo spettro è solo la premessa per realizzare il colore rosso. Riprova ne è che un cieco il quale padroneggia  teoria dei colori nella versione del realista diretto non sa ha alcuna idea di cosa sia il colore rosso. Questo, evidentemente, perché la teoria dei colori che il realista diretto è costretto ad abbracciare è decisamente incompleta privata com’è del suo aspetto fenomenico.

C’è poi la questione dello scetticismo: il realista diretto teme che il realista indiretto sia facile preda degli scettici, per questo respinge la sua teoria così adatta a dar conto delle illusioni e delle allucinazioni. Lui, per contro, si ritiene tutelato dal principio di credulità: cio’ che appare è cio’ che è fino a prova contraria. Ma questo principio è adottabile anche dal realista indiretto: il messaggio dei sense data è prima facie fedele alla realtà esterna. Una volta posto il principio di credulità, perché mai il realista indiretto dovrebbe essere più esposto agli attacchi dello scettico? Lo scettico puo’ dire al realista indiretto che i sense data non sono affidabili così come puo’ dire al realista diretto che è in contatto solo con delle apparenze. Entrambi si difenderanno con il principio di credulità: stessa difesa, stessa attaccabilità.

Quanto alla seconda obiezione posta nei confronti del realismo indiretto: dove risiedono i sense data? Risposta: nella coscienza (o nell’anima). Il realista indiretto, in questo senso,  è un dualista. E’ questo un grave inconveniente? No, al contrario, negare l’esistenza di questo “spazio” è impresa disperata: non c’è niente che conosciamo più intimamente dell’esperienza cosciente, anche se non c’è niente che sia più difficile da spiegare.