Here’s a short essay I wrote for my philosophy class called “Topics in Language and Mind.” This essay is essentially about the nature of perception, the central proposition of the Argument from Illusion being that objects that we perceive are entities separate from the physical objects which cause those perceptions. “Sense-datum” are the manifestations of the information our senses perceive about the actual, physical world. In other words, sense-datum are objects that we actually perceive as opposed to the objects which our perceptions gather data on (i.e. real world objects).
I believe that the most compelling version of the Argument from Illusion, as put forth by Smith, is its strongest version, which claims that the physical world is impossible to perceive directly. This version of the argument takes as its first premise the notion that perceptual illusions (i.e. cases of perception in which the object of perception does not exactly match the physical object which it is meant to represent) are possible for any modality. The second part of the argument, its most contentious part, claims that when a perceptual illusion occurs, that is, when one is perceiving something different than what is really there, there exists an object that actually possesses those illusory features. The third part goes on to conclude that because the physical object does not actually have the illusory features of the object of perception, the physical object is not being directly perceived.
I agree with the notion that no physical object could ever be perceived in a pure, direct way. There are many reasons to believe this, but for the sake of an argument which I wish to pursue, I will make a claim with respect to physics. It is impossible to be directly aware of an object’s actual state because there is a gap of time, albeit extremely miniscule, but significant nevertheless, that exists before a perception is made. The length of this gap is determined by a number of factors, including the speed of the phenomenon which our senses perceive (e.g. the speed of light, the speed of sound) and the speed of electrical signals from the sense organ to the brain. If we treat the phenomenon by which we perceive the world (e.g. light, vibrations in the air, heat) as raw, unprocessed data, then any transformation to this data will have an effect on the way this data is represented in our perceptual field. This is true because the objects of our perceptual field, the “sense-datum,” is entirely specified by the nature of this data. The gap of time between when the data pertaining to some physical object is created (e.g. light impinges off the object) allows for many sorts of transformations. Consider, for example, light perception. The sense data undergoes transformation when the light passes through gas (the air), when the light passes through the eye, when the eye creates an electric signal, and finally when the brain processes said electrical signal. Every transformation along the way is significant in that the original data pertaining to the physical object which we wish to perceive is immutably changed in some way, regardless of whether this change is insignificant or significant. Therefore the “sense-datum” that comprises the world of our perceptions can never precisely resemble the actual, physical objects which the sense-datum purports to represent.
With this in mind, I would like to point out a flaw in the general scheme of the Argument. Every step in the process of perception involves the transformation of data (even, say, when light impinges off an object), the final transformation being the change from electrical signal to perceptual experience. If we consider the incompatibility of our sense-datum with the physical world which it represents (i.e. illusions) as being only the result of this series of transformations, then there is a sense in which the actual, physical world is being perceived in as direct a manner as is possible. I say this because, if we go along the series of transformations, starting at the transformation of the electric signals in the brain to perceptual experiences, and reverse each one in order, we find that we can obtain pure, direct information about the physical object such as the object’s reflective character, its heat conductivity, or its hardness. In other words, pure data about the properties of physical objects is in fact directly perceived, but said data lies underneath a mess of other, inevitable data transformations that occur at every step in between the creation of this pure data and its final transformation into a perceptual experience. Essentially my claim is that the Argument is indeed correct in saying that no physical object could ever be directly perceived (i.e. that we could never have pure data about a physical object), but it is somewhat flawed in its claim that what is represented in our perceptual field is something entirely different than the physical object; the physical properties of the object are directly represented, though in a garbled and transformed way, such that we perceive the existence of illusions.