To assert that one’s own or someone else’s perceptual experience is nonveridical is normally to complain about it. Misperceptions in the properly functioning perceptual machine imply the frustration or potential frustration of an epistemic aim by what might be called a perceptual deranger. The reference to reality as something that can be matched is however misplaced for reasons discussed earlier. Mark Changizi says that illusions occur when ‘our brains attempt to perceive the future, and those perceptions don’t match reality’. I perceive the moon at the horizon as an enormous disk, what sort of tally with the physical measurement of the moon, which is 2,159 miles wide and 238,000 miles away, does my experience have that it does not have when I perceive the moon as a very small disk overhead.
Wikipedia says that illusions, one type of false perception, occur when ‘he information gathered by the eye is processed in the brain to give a percept that does not tally with a physical measurement of the stimulus source’.
VERIDICAL PERCEPTION DEFINITION WINDOWS
Birds with normal vision fly into plate glass windows misperceiving them as empty space. Other animals experience misperceptions and illusions. They fall into the categories of ‘misperceiving’ and having illusions. There are, however, certain products of the normally operating human perceptual system that can be considered ‘false’, just as some products of the normally operating but temporarily deranged human digestive system can be considered ‘bad’. As the sun rises and sets over the course of a day, the perceived colour of my walls changes, but there is no single instant of the day when they look the colour they really are, while in every other instant they do not. The same thing can look different from different angles and at different times and none of its appearances need be considered false or deceptive. Most perceptual experiences arising from the operations of a normally operating human perceptual system are ‘true’, just as most products of a normal human digestive system are from the biological perspective ‘good’. Snow White, who possesses a properly functioning perceptual system, has a veridical visual perception of a ripe apple, that she reaches for eagerly and appropriately, but it is not conducive to the preservation of her body. But it will not work to characterize true perceptions as those conducive to the preservation of the body and false perceptions as harmful and deleterious. For the time being, this machine is out ofservice and is likely to get hurt if others do not protect it. The hallucinating perceiver on LSD or suffering from delirium tremens is an improperly functioning perceptual system. Note that the products of a normally operating digestive system-the so-called chyme and chyle as well as various waste products-do not match or resemble anything that is not another product of a normally operating digestive system. Inputs and delivering slightly different outputs, some less efficient or competent than others, but none that put their possessors at a serious disadvantage for life. In both cases-perception and digestion-the tag ‘properly functioning’ applies to a range of systems that function in slightly different ways, taking somewhat differentįourth Set of Replies, AT vii. To pick up the thread of the argument, we can define a ‘properly functioning human perceptual system’ quasinormatively as a system that has arisen in the course of evolution and proved to be good enough for the health and survival of human beings in the same sense in which the ‘properly functioning human digestive system’ has arisen in the course of evolution and proved to be good enough in the same way.
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