In philosophy of perception, as well as in theory of knowledge, direct realism and indirect realism are two distinct theories which have in common to assume the existence of a world independent of us, of which we can know thanks to our sensory systems.
The question is whether the world can be perceived directly or not, in other words, whether or not mental contents present to us the world as it exists independently of our mind. For supporters of direct realism, the contents of perception are the very things of the real world; while for the defenders of indirect realism, the contents of perception are things at least in part dependent on the subject who experiences them.
Today there is a controversy between these two conceptions which opposes, on the one hand, those who possess the content of perceptual experience – what we perceive – as a mental entity or as a dependent representation of the mind (indirect realism), and, on the other hand, those who refute the notion of mental intermediary between the mind and the world (direct realism).
Certain philosophers, including A. D. Smith, maintain that this problem constitutes the principal philosophical problem concerning perception, raised as much in the psychological literature as in the philosophical literature. It is a question of answering at the same time a crucial epistemological question: “What can we perceive and know about the world?”; and to an essential metaphysical question: “What is the nature of what we perceive?”.
Direct realism is the thesis that the content of a state of perception consists of objects, properties or events of the world as it exists in itself, independent of the mind. Perception is interpreted as an opening onto this reality.
“Direct” means that in perceptual experience the world is given to the subjects without any mediation. In this sense, direct realism is a philosophical position which reinforces “common sense”. This notion also has the character of immediacy and automatism of perceptual experience, which imposes itself spontaneously on our consciousness without manifesting the underlying cerebral mechanisms: however complex the neurophysiological machinery that allows us to do experience of the world, it is completely invisible or hidden. This is what allows us to perceive, but it is not a part of what we perceive.
In contemporary philosophy, realism corresponds directly to the point of view developed by the “disjunctive” theory, or “disjunctivism”. This theory rejects the “conjunctive” interpretation of the illusion argument, in other words, the interpretation that an illusion indistinguishable from authentic perception is of the same type of mental state as itself. According to disjunctive theory, even though an illusory experience may make me mistakenly believe that I really perceive something, the two types of experiences are essentially different. Unlike illusion, in fact, authentic perception depends essentially on its object as part of the physical world. It would therefore not be fair to verify the perception of the world with a subjective experience presenting us with mere appearances. On the contrary, it is with the object perceived that the content of perception is identified.
According to this radical version of realism, perceptual experience is in a way “transparent”: the content it presents is the fact itself, perceived without an intermediary. In this sense, perception is not true in the sense that a message is transmitted by an emissary, according to the image given by D. Davidson, but in the sense that it puts the subject directly in relation to facts.
Indirect realism is the thesis according to which the world is perceived indirectly by contents of perception. This thesis stems from a consideration that conforms, not to “common sense”, but to scientific “good sense”: the world is given to our consciousness through the intermediary of the senses.
Although we have good reason to believe that our senses are reliable, they are nevertheless dependent on particular conditions such as the surrounding environment, our position in space, or distance, for example. On the other hand, our perception of the world is determined by internal factors related to the functioning of our sensory systems, so that everything we perceive is the consequence of what is going on in our mind or our brain.
Perception is therefore not a neutral and impersonal point of view on the world: it is always the particular point of view of a subject on the world. In addition, the subject’s experience of the world differs from what modern sciences and physics teach us in particular: the world we perceive is indeed full of colors, smells, sounds, etc., as well that of all kinds of qualities which do not exist as such in the objective world of physics.
Based on these two observations, indirect realism maintains that a perception is always the experience of a partly subjective “phenomenal” reality. If I see a red flower, then I experience a red flower that exists physically. The phenomenal character (appearance) of what is thus perceived does not depend directly on the physical existence of the object but rather on the type of mental state in which we find ourselves when we experience such object.
Indirect realism has been associated since the beginning of the 20th century with the theory of sense-data. In The Problems of Philosophy (1912), Bertrand Russell proposed to consider “my knowledge of the physical table” which is in front of me as a descriptive knowledge made possible by my direct knowledge of the sense-data which I experience when I see this table. According to Russell, our experience does not tell us about the nature of the physical world but about its structure, because our experiences are systematically connected to the world according to specific causal laws. It is therefore possible to know (by description) the physical object of the table that causes my visual sense-data, although it is not possible to have the representation.
Indirect realism makes it possible to account for the difference between a true experience and an illusion. All experience is causally related to physical objects, but the illusory experience is not caused by the same elements of the world that are generally associated with sense-data. This moderate form of realism also has the advantage of conforming to the scientific view of the world, which is radically different from our experience of it with our senses.
Difficulties of the two positions
The most frequently exposed problem with direct realism is that it does not seem able to offer a satisfactory explanation for illusions. Disjunctive theory in particular creates an ontological gulf between mere appearances and what is, between subjective experience and perception. Moreover, the very idea that the content of an experience constitutes an object existing independently of the mind is difficult to reconcile with the widely held idea that the content of perceptual experience is determined in part by mental processes which take place in our mind or brain.
The most important problem with direct realism, however, lies in its apparent incompatibility with the scientific conception of a physical world, a world where objects as we perceive them (with their colors, their apparent shape etc.) do not exist and are replaced by counter-intuitive scientific concepts (electromagnetism, force fields, etc.). Direct realism is also difficult to reconcile with the discovery of the (limited) speed of light, which implies, for example, that a star visible several light years away does not appear to our eyes as it is, but as it has been in the past several years ago.
The most important problem with indirect realism is that it seems to be linked to the thesis of the existence of sense-data, entities which do not find their place in the physical world. In addition, indirect realism would postulate the existence of a “veil of perception”, a curtain that interposes itself between our consciousness and the world, with metaphysical, epistemological and semantic consequences unacceptable to defenders of direct realism. The epistemological consequence would be skepticism, the impossibility of knowing the world itself. The metaphysical consequence would be the body / mind dualism, the return to the idea that there are non-physical entities. The semantic consequence would be the impossibility of referring to anything real or physical.
To go beyond this alternative, Edward J. Lowe proposes to distinguish between the concept of “being dependent on the mind” and the notion of “being a mental state”. According to Lowe, the contents of perception are dependent on the mind, but they are not mental beings. This distinction makes it possible to reconcile the subjective and objective dimensions of perception by accounting both for the representative and constructive nature of perceptual contents (insofar as they are “dependent on the mind”), and for their exteriority in relation to to the mind (insofar as they are not “mental beings”).
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