Image courtesy Wikibooks: Consciousness Studies
Direct Realism is the notion that what we touch and see are directly things in the world. When he looks at an object the Direct Realist does not believe that he is seeing an image on his retina or some activity in his brain, he believes he is seeing the thing itself, directly.
We know from physics that sight is mediated by the light that is reflected from the objects in the world around us and that these objects are separate from other things as a result of the short range electrical forces that they exert. In proposing direct perception the Direct Realists are implying that their experience is directly the interaction between photons and the close range electric forces that make these photons change direction and that touch is the short range forces acting on their finger etc.
Direct Realism implies that somehow perception extends along the path of the photon to the electrical field that made the photon turn in the general direction of the viewer. Similarly, when a Direct Realist hears a sound they believe that this sound is directly connected to the vocal chords of the speaker, this implies that some mysterious influence travels between the molecules of air to extend their perception directly into contact with the inside of someone's larynx.
Now, these implied beliefs would be hilarious if it were not for the fact that many modern philosophers, psychologists and even some neuroscientists are Direct Realists.
The science of perception shows that there is no advantage whatever in assuming that we perceive objects directly. There is no evidence of any sort for the extension of the human mind into the vocal chords of other people. There are no documented, causal effects of a person's mind or thoughts on the point where light rays are bent, out there in the world. Furthermore, there is strong evidence for perception being based on a representation of the world in the brain. This evidence ranges from the neurophysiology of perceptual "filling in", through the neural basis of dreams to the cerebral cortical modelling of motion.
The neural location of perception can even be observed without neurophysiological experiments. For example, when we rapidly shift our gaze the whole view does not change chaotically like the image from a crazed amateur's movie camera, the update of the data in the brain is suspended during the shift of gaze to avoid this problem. When we look at ourselves in a mirror we can never see our eyes move. So where are the steady, reflected eyes that appear to be in the mirror when we shift our gaze? It is obvious that we have a stable interior view that is updated by the senses, not a direct connection with objects beyond our body. Why not try it, look in a mirror and ask yourself what you are seeing whilst your eyes move, do you really see the world itself or a representation of a reflection, a model in your brain?
Direct Realists seem to be trying to explain our apparent separation from the things that we observe in terms of the actual space between our sense organs and the things that give rise to the disturbances that excite these organs. But we do not see the world like this, we see it like an image that is separated from us, not as 3D objects in a space. That's why television and photos are so comprehensible - they offer the world in a form that is like our retinal images. We do not perceive sounds as coming from the depths of a speaker's vocal chords, we perceive them as coming from the direction of their heads and, furthermore, we perceive sounds to come from people's heads even if we hear the sounds through headphones and even if the speaker is merely an image on a screen. Some piece of physics in our brain binds the sense of sound to a geometrical form that hosts the image.
What disturbs me about the direct/indirect realism debate is the assumption from the outset that the "real world" is like our experience. The direct realists make the assumption that what is real is what we see. It isn't, measurements tell us that the world itself is mainly space and organised in at least 3+1 dimensions. If our experience is "like" anything at all it is like the two dimensional images that occur if the tiny component of the world called light is projected onto a surface using a lens system, not like the world itself.
Direct Realists should make it clear that they believe that the contents of experience are directly out there in the world. The direct realist/indirect realist debate should always begin with "see these things that are in your conscious experience, as a Direct Realist I believe these are actually a type of electrical force right out there in that street". It would then be obvious that Direct Realism still has an Explanatory Gap - how are some short range forces the colour "red" and others the texture "rough" given that the short range forces are similar in both cases? It would also be obvious that there is still a problem with Aristotle's regress - OK there is a set of forces out there but how do these become seen without recursion or regress? However, most importantly, it would be obvious that the idea is absurd from the outset, of course your mind does not stretch into the street.
Direct Realism is particularly disingenuous because it offers no explanation of how a pattern of electrical activity that bends light rays could become a view containing the world around us. It does not explain Aristotle's regress but just shifts the problem to another location with the contents of mind placed out in the world instead of in the brain. Even if Direct Realism were true it would provide no answers to the problems that confront us in the neuroscience and philosophy of mind.
So Direct Realism is absurd and explains nothing, it does not ask how our perception might arise but instead begins with the prejudice that our perception is directly the things in the world and attempts to fit perception to this model, simply denying any features that contradict Direct Realism as non-physical. Why would anyone take such an unscientific approach? The reasons are multiple from a mistaken impression that Direct Realism is more compatible with theology than other ideas (Reid) to a desire to justify the claims of "strong AI" (Dennett). Although Dennett also makes the mystical suggestion that what we experience is in some sort of "logical space" (See There is no information without representation). This would all be rather amusing if it were not for the fact that Direct Realists are evangelical and seem to believe it is their duty to suppress all other ideas.
Perhaps, when Direct Realists lie down and shut their eyes, they sense a dark space, if so they might ask how such a thing occurs. How does this volume of simultaneous darkness surrounding a point occur? They might consider this whilst watching this non-existent green dot race around the ring without moving:
Green afterimage courtesy Wikimedia Commons.Stare at the cross in the picture and you will see a (non-existent) green dot racing round the image.
Or perhaps the Direct Realist could explain reverse causality - see SENSORIMOTOR ADAPTATION TO VIOLATIONS OF
Alex Holcombes web page http://www.psych.usyd.edu.au/staff/alexh/