Direct and indirect realism
In the philosophy of perception and philosophy of mind, direct or naïve realism, as opposed to indirect or representational realism, are differing models that describe the nature of conscious experiences. The debate arises out of the metaphysical question of whether the world we see around us is the real world itself or merely an internal perceptual copy of that world generated by our conscious experience.
Indirect perceptual realism is broadly equivalent to the scientific view of perception that subjects do not experience the external world as it really is, but perceive it through the lens of a conceptual framework. Furthermore, indirect realism is a core tenet of the cognitivism paradigm in psychology and cognitive science. While there is superficial overlap, the indirect model is unlike the standpoint of idealism, which holds that only ideas are real, but there are no mind-independent objects.
Conversely, direct perceptual realism postulates that conscious subjects view the world directly, treating concepts as a 1:1 correspondence. Furthermore, the framework rejects the premise that knowledge arrives via a representational medium, as well as the notion that concepts are interpretations of sensory input derived from a real external world.
History
was the first to provide a description of direct realism. In On the Soul he describes how a seer is informed of the object itself by way of the hylomorphic form carried over the intervening material continuum with which the eye is impressed. In medieval philosophy, direct realism was further defended by Thomas Aquinas.Indirect realism was popular with several early modern philosophers, including René Descartes, John Locke, G. W. Leibniz, and David Hume.
Locke categorized qualities as follows:
- Primary qualities are qualities which are "explanatorily basic" – which is to say, they can be referred to as the explanation for other qualities or phenomena without requiring explanation themselves – and they are distinct in that our sensory experience of them resembles them in reality. Primary qualities cannot be removed by either thought or physical action, and include mass, movement, and, controversially, solidity.
- Secondary qualities are qualities that one's experience does not directly resemble; for example, when one sees an object as red, the sensation of seeing redness is not produced by some quality of redness in the object, but by the arrangement of atoms on the surface of the object which reflects and absorbs light in a particular way. Secondary qualities include colour, smell, sound, and taste.
Late modern philosophers, J. G. Fichte and G. W. F. Hegel followed Kant in adopting empirical realism. Direct realism was also defended by John Cook Wilson in his Oxford lectures. On the other hand, Gottlob Frege subscribed to indirect realism.
In contemporary philosophy, indirect realism has been defended by Edmund Husserl and Bertrand Russell. Direct realism has been defended by Hilary Putnam, John McDowell, Galen Strawson, and John R. Searle.
However, epistemological dualism has come under sustained attack by other contemporary philosophers, such as Ludwig Wittgenstein and Wilfrid Sellars in his seminal essay "Empiricism and the Philosophy of Mind". Indirect realism is argued to be problematical because of Ryle's regress and the homunculus argument. Recently, reliance on the private language argument and the "homunculus objection" has itself come under attack. It can be argued that those who argue for "inner presence", to use Antti Revonsuo's term, are not proposing a private "referent", with the application of language to it being "private" and thus unshareable, but a private use of public language. There is no doubt that each of us has a private understanding of public language, a notion that has been experimentally supported; George Steiner refers to our personal use of language as an "idiolect", one particular to ourselves in its detail. The question has to be put how a collective use of language can go on when, not only do we have differing understandings of the words we use, but our sensory registrations differ.
Arguments against direct realism
Argument from illusion
This argument was "first offered in a more or less fully explicit form in Berkeley." It is also referred to as the problem of conflicting appearances. It has been argued that "informed commonsense" indicates that perceptions often depend on organs of perception. For example, humans would receive visual information very differently if they, like flies, had compound eyes, and may not even be able to imagine how things would appear with entirely different sense organs such as infra-red detectors or echo-location devices. Furthermore, perception systems can misrepresent objects even when in full working order, as shown, for example, by optical illusions like the Müller-Lyer illusion. More dramatically, sometimes people perceive things which are not there at all, which can be termed instances of "hallucination" or "perceptual delusion".Image:Double-alaskan-rainbow.jpg|thumb|upright=1.15|Illusions are present in nature. Rainbows are an example of a perceptual delusion. "For, unlike an architectural arch, a rainbow recedes as we approach it, never to be reached."
The argument from illusion allegedly shows the need to posit sense-data as the immediate objects of perception. In cases of illusion or hallucination, the object has qualities that no public physical object in that situation has and so must be distinct from any such object. Naïve realism may accommodate these facts as they stand by virtue of its very vagueness : it is not specific or detailed enough to be refuted by such cases. A more developed direct realist might respond by showing that various cases of misperception, failed perception, and perceptual relativity do not make it necessary to suppose that sense-data exist. When a stick submerged in water looks bent a direct realist is not compelled to say the stick actually is bent but can say that the stick can have more than one appearance: a straight stick can look bent when light reflected from the stick arrives at one's eye in a crooked pattern, but this appearance is not necessarily a sense-datum in the mind. Similar things can be said about the coin which appears circular from one vantage point and oval-shaped from another. Pressing on your eyeball with a finger creates double vision but assuming the existence of two sense-data is unnecessary: the direct realist can say that they have two eyes, each giving them a different view of the world. Usually the eyes are focused in the same direction; but sometimes they are not.
However, this response is presumably based on previously observed data. If one were to be able to observe nothing other than the stick in the water, with no previous information, it would appear that the stick was bent. Visual depth in particular is a set of inferences, not an actual experience of the space between things in a radial direction outward from the observation point. If all empirical evidence is based upon observation then the entire developed memory and knowledge of every perception and of each sense may be as skewed as the bent stick. Since objects with different qualities are experienced from each of the different perspectives there is no apparent experiential basis for regarding one out of any such set of related perceptual experiences as the one in which the relevant physical object is itself immediately experienced. The most reasonable conclusion is that the experienced object is always distinct from the physical object or at least that there is no way to identify which, if any, of the immediately experienced objects is the physical object itself. Epistemologically it is as though physical objects were never given, whether or not that is in fact the case.
Another potential counter-example involves vivid hallucinations: phantom elephants, for instance, might be interpreted as sense-data. A direct realist response would differentiate hallucination from genuine perception: no perception of elephants is going on, only the different and related mental process of hallucination. However, if there are visual images when we hallucinate it seems reasonable that there are visual images when we see. Similarly if dreaming involves visual and auditory images in our minds it seems reasonable to think there are visual and auditory images, or sense-data, when we are awake and perceiving things. This argument has been challenged in a number of different ways. First it has been questioned whether there must be some object present that actually has the experienced qualities, which would then seemingly have to be something like a sense-datum. Why couldn't it be that the perceiver is simply in a state of seeming to experience such an object without any object actually being present? Second, in cases of illusion and perceptual relativity there is an object present which is simply misperceived, usually in readily explainable ways, and no need to suppose that an additional object is also involved. Third, the last part of the perceptual relativity version of the argument has been challenged by questioning whether there is really no experiential difference between veridical and non-veridical perception; and by arguing that even if sense-data are experienced in non-veridical cases and even if the difference between veridical and non-veridical cases is, as claimed, experientially indiscernible, there is still no reason to think that sense-data are the immediate objects of experience in veridical cases. Fourth, do sense-data exist through time or are they momentary? Can they exist when not being perceived? Are they public or private? Can they be themselves misperceived? Do they exist in minds or are they extra-mental, even if not physical? On the basis of the intractability of these questions, it has been argued that the conclusion of the argument from illusion is unacceptable or even unintelligible, even in the absence of a clear diagnosis of exactly where and how it goes wrong.
Direct realists can potentially deny the existence of any such thing as a mental image but this is difficult to maintain, since we seem able to visually imagine all sorts of things with ease. Even if perception does not involve images other mental processes like imagination certainly seem to. One view, similar to Reid's, is that we do have images of various sorts in our minds when we perceive, dream, hallucinate and imagine but when we actually perceive things, our sensations cannot be considered objects of perception or attention. The only objects of perception are external objects. Even if perception is accompanied by images, or sensations, it is wrong to say we perceive sensations. Direct realism defines perception as perception of external objects where an "external object" is allowed to be a photon in the eye but not an impulse in a nerve leading from the eye. Recent work in neuroscience suggests a shared ontology for perception, imagination and dreaming, with similar areas of brain being used for all of these.
The character of experience of a physical object can be altered in major ways by changes in the conditions of perception or of the relevant sense-organs and the resulting neurophysiological processes, without change in the external physical object that initiates this process and that may seem to be depicted by the experience. Conversely any process that yields the same sensory/neural results will yield the same perceptual experience, no matter what the physical object that initiated the process may have been like. Furthermore, the causal process that intervenes between the external object and the perceptual experience takes time, so that the character of the experience reflects, at the most, an earlier stage of that object than the one existing at the moment of perception. As in observations of astronomical objects the external object may have ceased to exist long before the experience occurs. These facts are claimed to point to the conclusion that the direct object of experience is an entity produced at the end of this causal process, distinct from any physical object that initiates the process."