For example, there are cases where people have lost, say, their ability to perceive colors, or have lost depth perception or parts of their visual field. Thus such people will have different visual experiences than normally. In fact, simply putting on shaded glasses or lens with altered curvatures will enable you to perceive objects with qualities that are other than the qualities the objects really have. (Let us keep in mind our definition of perceptual illusion: The term “illusion” is to be understood as applying to any perceptual situation in which a physical object is actually perceived, but in which that object perceptually appears other than it really is, for whatever reason.)
Another common class of cases is the case of glasses. What I mean by this, as no one has yet discovered the secret of eternal youth, as we grow older, and due to the nature of gravitational effects or other factors, many of us discover that our eyes gradually loose their visual acuity. Corrective lenses are required (or laser treatment, etc.). For example, if I look at a page of a book without my reading glasses on, all I see is what looks like smudges of ink and random patterns of spaces. But with glasses on, what before was clear as mud becomes as clear as day. Similar experiences occur with distant night vision. If I look at arrays of lights in the distance without distance glasses, each light source doubles or triples and there is much glare. They also move to and fro or tilt as I move my head. But with glasses, the pairs and triples of lights become immovable single light sources with hardly any glare. So in these cases, the glasses enable one to perceive what is really the case, whereas the weakness of the naked eye creates an illusionary situation. Notice that to meet the criteria of “illusion” as I have defined it; it is irrelevant whether you tricked or fooled in the illusionary situation. All that matters is that the appearance is other than the reality. We all recognize, I presume, the common sense distinction between appearance and reality.
The evidence is overwhelming in support of the proposition that illusion (and hallucination) is possible. Indeed, we are warranted in the stronger claim that illusion (and hallucination) is a common occurrence in our awareness, or perceptual interaction with the world. Although I have focused, for simplicity, on our visual sense modality, research shows that every sense is subject to a wide range if illusions or hallucinations in their employment.
These claims come as no surprise for at least two reasons. For one, and confining my remarks to the sense of sight, the medium, between our sense receptors, the eyes, and the external objects perceived, is constantly changing, and these changes are directly correlated to the nature of our sense fields — to what we see. From dawn to dusk, to dawn again, the play of light and atmosphere presents a kaleidoscope of changing hues throughout the day. In the darkest night, and in the absence of artificial light, colors disappear altogether, or to gradually return with the dawn. Moreover, besides the effects of our spinning turning planet in relation to the sun, our own mobility on the planet involves changing points-of-view or perspectives with respect to the objects we perceive.
The second reason concerns the intricate neurological structures of our central nervous system, including the brain. The complexity and subtlety of such systems, from encoding the information that impinges on our sensory receptors to the final destination in specific areas of the brain are truly awesome. However, any malfunction or intervention at any point in the process correlates precisely with distortions or illusions in our sense fields.
Considering the above facts, philosophers and other thinkers have drawn some startling conclusions. In particular, the claim has been made that in light of the fact that illusion is undeniably possible, our perceptual relationship to the external world is very different than what our common sense intuitions lead us to believe. In fact, the claim goes further to maintain that any direct perceptual access to an independently existing reality is impossible. To see why this is so will be the topic of my next article.
Puzzle
1. In the days of the horse and wagon, there was a town picnic, and the whole town participated. They all jumped on the wagons available, the same number in each. On the way to the picnic field, 10 of the wagons broke down, and each remaining wagon had to carry 1 additional person. On the way back 15 wagons broke down, but all made it back, as each wagon left took on 3 more people each. So how many went to the picnic?
Answer to last week’s puzzle
1. Eight hours, 18 minutes, 27 and 9/13 seconds.
