Gregory on the Grand Illusion

It is sometimes said that all perception is a grand illusion. But this does not help. We may be driven into saying that 'everything is illusion', but this is as pointless as saying 'everything is a dream'. For when applied to everything, the words 'dream' and 'illusion' cease to have meaning. We need contrasts for seeing, and contrasts for describing and thinking. To claim that there is an illusion, there must be some contrasting non-illusion. This applies across the board. If every object were red there would be no point in seeing red, or using the word 'red'.

What are illusions?  

We may say that illusions are departures from reality-but what reality? Appearances are very different from deep realities of physics. If these are taken as reference truths we would have to  say that all perceptions are illusions. This is as pointless as saying that perception is a dream.  Illusions are judged with simple common-sense ideas of physics, and measured with kitchen instruments: rulers, clocks, scales, thermometers, and so on. We might define illusions as deviations from kitchen physics. (Gregory, 2009, pp. 9-10).

I think this is a disappointing reply to the idea of the grand illusion: "To claim that there is an illusion, there must be some contrasting non-illusion."  All of vision could be a grand illusion if all visual perception were a deviation from kitchen physics.  (Set aside the worries one might have about this definition.)  The contrast would be if a visual perception were not a deviation from kitchen physics.  I would think that the illusion/non-illusion distinct only requires a conceptual or theoretical distinction or a logical possibility of something that is an illusion and something that is a non-illusion.  We seem to have this.  We do not, however, require positive instances of both illusions and non-illusions.

Gregory Really Rejects the Homunculus

For many years, the inversion of the retinal image seemed to be a serious problem: do babies have to learn to correct the inversion, to see things the right way up? This question is based on the false notion that the brain is a kind of eye looking at the retinal image, which presumably has its image-with another eye, another image, and so on forever. This notion of an inner eye should have been a non-starter as it can never get anywhere. The point is, one's retinal image is not seen, as an object is seen. The retina is the interface between the optical projection from objects to the neural-coded signals to the brain-arriving down the million fibres of the optic nerve-which are related to touch experience of objects. The inversion in the image does not matter: what matters is the relation of the brain's visual signals to those from touch. Indeed without touch retinal images would have little or no meaning.(Gregory, 1997, pp. 52-53).

Here Gregory presents the inferentialist view of visual images quite succinctly: "one's retinal image is not seen, as an object is seen".  As we shall see, this is the way around the problems Gibson sometimes describes has with retinal images.

I do wonder if Gregory had all this stuff down in earlier editions of Eye and Brain.  I would guess that he did, but our local copy of the first edition from 1966 is checked out.

Gregory's Brainy Mind

Another quick read from Gregory is here.

Gregory's Case for Filling In

A free online version.

Gregory Recalls S.B.

An interesting note from Nature from a while ago. Many readers of this blog will know of S.B. (Sidney Bradford) by way of Alva Noë's Action in Perception.  Bradford was one of the  congenitally blind individuals who had corneal grafts in adulthood.  Noe interpreted this case as an illustration of "experiential blindness".

Gregory believes S.B.'s case provides a positive answer to the Molyneaux question.

Gregory on Intelligence from Perception

This philosophy, or paradigm, is largely derived from Helmholtz. It is, that visual and other perception is intelligent decision-taking, from limited sensory evidence. The essential point is that sensory signals are not adequate for direct or certain perceptions; so intelligent guessing is needed for seeing objects. The view taken here is that perceptions are predictive, never entirely certain, hypotheses of what may be out there.
     It was, perhaps, the active intelligence of perception that was the evolutionary start of conceptual problem-solving intelligence. (Gregory, 1997, p. 5).

While Gregory does not "do anything" about this idea of problem-solving intelligence evolving from perceptual intelligence, there seems to be nothing in at least his conception of intelligent vision that precludes this.

Gregory on Active Perception

What is striking is the huge amount of brain contributing to vision, giving immense added value to the images of the eyes. Where does this extra richness for vision come from? By some authorities it is simply denied-they see perception as passive acceptance of what is out there, as a window facing the world. But this does not begin to explain how we see objects from the sketchy images of the eyes, even from sparse lines and crude dots of seemingly inadequate pictures. In ideal conditions, object perception is far richer than any possible images in the eyes. The added value must come from dynamic brain processes, employing knowledge stored from the past, to see the present and predict the immediate future. Prediction has immense survival value. It not only makes fast games possible in spite of the physiological signal delays from eye to brain, and brain to hand. Anticipating dangers and potential rewards is essential for survival¬made possible by buying time from seeing objects distant in space. (Gregory, 1997, p. 2).

I am assuming that EPists are among the "authorities" here.   I think the perception as passive idea comes from the talk of direct pickup; there is no activity of inference or computing.  For EPists the activity of perception is moving the eyes and body around, but that thereafter the visual system just lets the information seep in. 

For Gregory, there is the activity of moving the eyes and body (I assume he's ok with the movements of the body.  The eye he discusses briefly (p. 44f)).  The interesting perceptual activity for Gregory, however, is in the brain.

Gregory: The Visual System is Part Camera, Part Not-Camera

As I noted in comments to a previous post, Gregory's Eye and Brain seems to me to be a nice corrective to some of the caricatures of cognitivism.  It is a nice work on vision for a general audience.

The eye is a simple optical instrument. With internal images projected from objects in the outside world, it is Plato's cave with a lens. The brain is the engine of understanding. There is nothing closer to our intimate experiences, yet the brain is less understood and more mysterious than a distant star. 

         .....

Optical images were unknown before the tenth century, and not until the start of the seventeenth were images discovered in eyes. At last it became clear that light does not enter or leave the brain, locked privily in its box of bone. All the brain receives are minute electrochemical pulses of various frequencies, as signals from the senses. The signals must be read by rules and knowledge to make sense. Yet what we see, and what we know, or believe, can be very different. As science advances, differences between perceived appearances and accepted realities become ever greater.
     This is far beyond the common account that the eye is a camera; yet this is essentially true, though far from the whole story. It is the uncamera-like features of eyes and brains that most interest us here.  (Gregory, 1997, pp. 1-2).

When I read Gregory on this kind of thing, I take his critical target to be the views of scientists and philosophers from centuries ago.  With EP, I generally think that the critical targets are much closer to home, e.g. Gregory.

Gregory on Downplaying the Mystery of Inverted Vision

We now think of the brain as representing, rather as the symbols of language represent characteristics of things, although the shapes and sounds of language are quite different from whatever is being represented. Language requires rules of grammar (syntax), and meanings of symbols (semantics). Both seem necessary for processes of vision; though its syntax and semantics are implicit, to be discovered by experiment.
     Some puzzles of vision disappear with a little thought. It is no special problem that the eyes' images are upside down and optically right-left reversed-for they are not seen, as pictures, by an inner eye. (Gregory, 1997, p. 5).

Noë, and others, often suggest that upside down images are pseudo-problems that representationalism invokes.  But, Gregory pretty quickly dispenses with this putative problems.  He clearly presents them as only prima facie puzzling features of vision--features that might confuse common sense or early scientific theorizing, but ones that do not give rise to deep perplexity for representationalists.

Gregory also Rejects the Homunculus

There are many traps along the way of exploring Eye and Brain. It is important to avoid the temptation of thinking that eyes produce pictures in the brain which are perceptions of objects. The pictures-in-the-brain notion suggests an internal eye to see them. But this would need a further eye to see its picture-another picture, another eye-and so on forever, without getting anywhere. (Gregory, 1997, p.5).

I wonder if this was in the first edition, back in 1966.