Philosophy of Perception - In Defence of the Argument From Illusion

What do we perceive when we see, hear, think, smell and taste? Do we perceive the real objects or do we perceive the objects of perception? Do we ever truly experience the objective world?

The Argument From Illusion can be illustrated by a state which is one of genuine awareness of a world which may be indistinguishable from one which is mere appearance (Dancy, 1995). In other words, this argument states that we perceptually experience veridical, hallucinatory and illusionary experiences in the same manner. This can be further explored via two distinct principles, both of which support the premise that we perceptually experience veridical, hallucinatory and illusionary experiences in the same way.

The Common Kind Principle states that the experience we perceive applies when viewing an illusion, undergoing a hallucination or having a veridical experience. The Phenomenological Principle surrounds the appearance of things, or things as they appear in our experience, or the ways we experience things, thus the meanings things have in our experience (Smith, 2018). Therefore, if something appears, whether it be a hallucination, illusion or veridical experience, then there is something in which I experience. Another theory worth defining before exploring the strength of The Argument From Illusion against objections is a theory that supports it: Sense Datum Theory. 

The most popular response to the argument from illusion for most of the 20th century was to accept the argument, and its conclusion that the immediate objects of perception are always internal to the mind. The view which resulted was called ‘the sense datum theory of perception’, because the mind-internal things which were supposed to be the objects of perceptual experience were called ‘sense data’ (Speaks, 2006).

As well as exploring why The Argument From Illusion is a sound argument, objections must be considered and examined to produce support for the argument and examine the argument’s strength against these objections. 

The first issue is an epistemological objection questioning how we are to believe in real objects if we are to believe we perceive hallucinations in the same manner as veridical experience. The second objection is the richness of senses when perceiving veridical experience. The third objection comes from the theory of mind which is physicalism. This argues that what we perceive is wholly physical and therefore non-veridical experiences are not physical in nature (Huemer, 2019).

These objections will be considered as potentially effective objections which could examine how we perceive veridical, illusionary and hallucinatory perceptions better than The Argument From Illusion in which we experience these different manners of experience the same.

In Defence Of The Argument From Illusion

A scenario that seems to effectively defend the Argument From Illusion comes from Hilary Putnam who created the scenario below;

Let us suppose that someone, call her Helen, does have the (perhaps impossible, but let us assume it is possible) experience of having a dream that is so real it is exactly like being in a place; but a place that person has never been, say, in front of the Taj Mahal. The traditional sense-datum epistemologist argues thus: "Helen  is certainly experiencing something; what she is experiencing is certainly not the Taj Mahal (that is thousands of miles away) or indeed any physical object (her eyes are closed and the pillow is over her head); therefore, what she is experiencing is something mental. So the immediate object of a perception is, at least some of the time, something mental.” (Putnam, 1994; Reynolds, 2000). 

This sounds plausible in the sense that the idea that Helen is directly experiencing the Taj Mahal is squashed and instead theorised as a mental experience. The belief that objects of perception as different as a physical building (veridical experience) and a hallucinatory experience of a building are experienced exactly alike does not seem implausible here then (Putnam, 1994; Reynolds, 2000). So, if we are in support of this argument, we must state that what Helen is perceiving, whether it be the Taj Mahal in her dream or the actual Taj Mahal are both Sense Data. Therefore, even when Helen is dreaming of the Taj Mahal, she is experiencing something non physical or non veridical. The Argument From Illusion states that this experience is the same as experiencing something physically in front of you and therefore normal perception is the experience of sense data rather than the physical objects of perception. Thus, the object being experienced mustn’t have the exact same properties it appears to have. For example, Helen may experience parts of the Taj Mahal that it does not possess, both when dreaming of it and standing in front of it.

The Argument From Illusion holds both the Phenomenological Principle and the Common Kind Principle. Sense data are normally said to be phenomenal in nature (Reynolds, 2000), they are part of what it is like to have a dream or undergo an illusion and thus, the object we experience in a veridical perception is like for you what the object is like, which does not differ in nature whether experiencing an illusion or a veridical object.  

Epistemological Objection

It does seem problematic to state that what Helen is experiencing when dreaming is something like the Taj Mahal but if she was in front of the physical Taj Mahal, she would also be experiencing something like the Taj Mahal (Phenomenal Principle) or that the experience of dreaming of it (it being a mental object) is the exact same perpetual experience as veridically perceiving it. Logically and practically, it seems implausible as the objects one experiences are just different when undergoing an illusion rather than a veridical experience (Ayer, 1940; Reynolds, 2000). These Epistemological objections to Sense Data Theory are also objections to the Argument From Illusion. Helen dreaming of the Taj Mahal is logically a completely different perceptual experience than standing in front of it. In normal conversation, we would describe a veridical experience differently to an illusion, dream or hallucination so surely this must conclude that they are different perceptual experiences. This looks plausible as, it seems on the surface, if we are to believe that we experience real life and dreams, for example, in the same manner then what is stopping us from becoming sceptical of the real world? How can we be sure that the real world is out there if we perceive sense data in veridical and non-veridical experiences? This objection states that the Sense Data Theorist “…cannot account for our having the concept of physical objects, or for our ability to conceive of the properties of physical objects (Huemer, 2019). 

However, to experience a physical object is to have a sense datum that represents that object, so physical objects are seen (O'Shaughnessy 2003; Huemer, 2019). The objection above does not hold, as we know (or we think we know, depending on your view) about various aspects of the world without having perceptually experienced them. We perceive very little, in grand terms. We see a wooden table and know it was made from a tree but we do not perceive the tree. We know people have organs under their skin and yet, most of us never perceptually experience them. So, the argument that we cannot ascribe to Sense Data Theory or The Argument From Illusion due to the idea that we cannot be sure whether what we perceive is real or not may be true, but that doesn’t stop us from having knowledge about objects of perception or objects we cannot perceive.

This is examining the argument from a purely logical and objective stance. Perceptual experience is not logical or objective. Each one of us perceptually experience in different ways in accordance with many internal and external factors. One might experience the sound of an airplane flying over head as far away, whereas another might experience the sound as close. One might think of an orange and a small satsuma enters the consciousness, whereas another might imagine an orange on a tree. If I showed two people an orange, they would arguably both perceive it in more similar manners. However, in terms of experience, both the image of an orange in their minds when asked to imagine one and the image of an orange in front of them are both appearing in their consciousness. What we see in veridical experiences and thoughts, dreams and hallucinations all simply appear in our consciousness. Again, this is purely from an experiential stance. Therefore, if we can accept that visual experiences, auditory experiences (i.e. veridical experiences) and illusions, hallucinations, dreams and thoughts all appear in consciousness, then the Argument From Illusion contending that we experience all of these in the same way must be sound. Thus, the objection that, logically, we must experience illusions differently to veridical experience simply because they should be different perceptual experiences is too simplistic. I ask you to close your eyes and picture a dog. A dog appeared in your consciousness, most likely. Now open your eyes. The world that rushes into your consciousness appears out with your control, you cannot choose what’s there, just like a dog just appeared in your consciousness. Although, this thought experiment may just be proof that what we perceive simply appears, it should also be proof that we perceive veridical and illusionary experiences in the same manner. Further, consider the manner in which we cannot recall the dreams we experienced (or did not) the night before, in comparison with the inability to recall the majority of your thoughts from the day that just passed. Do we not experience these two scenarios in the same manner?

Richness Of Sensory Experience Objection

Another objection is the failure to experience all the senses in non-veridical experience. If we return to Helen’s real experience of the Taj Mahal in India, she would not just visually perceive the building, but the warmth of the sun or the smell of the sea air or the feeling of the wall she is sitting on. It would be naïve to assume that Helen could experience all of these sensory experiences via a dream or hallucination or simply thinking about the Taj Mahal. This is a stronger objection than the previous one in that it takes into account the subjectivity of experience without relying solely on the logic and objectivity of experience. We simply cannot perceive all the richness of sense data that we would experience while perceiving something veridically. 

I ask you to imagine an orange. Now attempt to imagine the smell of it or the feeling of it when holding it. Now, if I were to give you an orange in normal waking life, you could smell it and feel it more prominently. Is this not a strong verdict against the Argument From Illusion? Does this not conclusively portray that we do perceive veridical experiences differently to illusionary experiences? It seems to, when isolating perceptual experiences underwent via specific senses. However, if we are to be purely examining perceptual experiences, then the objection does not hold. If you ingested a hallucinatory drug and experienced the Taj Mahal, it would be unlikely that you could decipher between what is real and hallucinated. Therefore, this is a sound argument for the Argument From Illusion. We would experience a hallucination visually, and perhaps other sensory experiences, in the exact same manner as a veridical experience.

This can also be said regarding illusions. The following three premises could all be true;

1.     I see a car

2.     The car appears purple to me

3.     The car is blue

Since the car is not purple, I am not experiencing veridically or experiencing real life, therefore I am experiencing sense data. If premise 3 was “The car is purple,” would I not be experiencing perceptually the car in the same manner as the illusion of the car looking purple to me when it is blue. Although, there is nothing physical that is purple in front of me, I am perceiving something blue. Some theorists have argued that this set of premises dismisses the Argument From Illusion by stating that we have not been offered any reasons for concluding any sense data are purple (Greenberg 1977; Barnes and Broad, 1945). 

Although, Sense Data Theory states that what we perceive both in veridical and non-veridical experiences are mind-dependent and therefore, when I see the car as purple, that is a mind-dependent object of perception and therefore Sense Data. I form an image in my mind of a purple car or I form an image of a blue car. One is the real colour of the car but both experiences are experienced the same way as sense data. Hence why Sense Data theory accommodates both the Common Kind Principle, as we experience sense data both in veridical and non-veridical experiences, and the Phenomenological Principle, in that what it’s like to experience a veridical experience is the same as what it’s like to experience an illusion.

Physicalist Objection

Lastly, another objection comes from the physicalist theory. In this view, the world is entirely physical; mental states either do not exist or are reducible to physical states, such as brain states (Huemer, 2019). This fails to take into account the subjectivity of experience. It also does not account for consciousness. Consciousness is not a physical entity. 

Physical events are simply mute as to whether it is “like something” to be what they are. The only thing in this universe that attests to the existence of consciousness is consciousness itself; the only clue to subjectivity, as such is subjectivity (Harris, 2011).

Physicalist theories tend to focus on the internal, physical processes of the brain, whereas experience goes beyond the physical structures of the brain and objects (Chalmers, 1995; Harris, 2011). Since consciousness is not physical and we are not aware of the electrochemical events taking place at each of the trillion synapses in our brains (Harris, 2011), how can all mental states be explained via physical objects and how can consciousness be explained via physicalist theories when it is not physical.

Conclusion

I believe the Argument From Illusion holds strong in response to these three objections. By using epistemology as an objection, the point of the subjectivity of experience is missed. It is difficult (if not, impossible) to decipher what changes occur in the brain with regards to experience. The appearance of experience is a strong argument for the Argument From Illusion due to the acceptance of subjective experience. 

Lastly, the theory of physicalism states that what I experience is purely physical. It is a response to external, physical objects and illusions are in response to no physical things that have the properties that perceptually appear to us (Huemer, 2019). However, this again misses the subjectivity of experience. What we perceive in veridical experience is an appearance in consciousness, a consciousness that cannot be seen or observed in any physical sense. Illusions, dreams, thoughts and hallucinations also appear in consciousness, out with our control, so how can perceptual experiences appear within something non-physical but also be in response to physical objects in veridical experience but non-physical objects in non-veridical experience? This seems implausible given the different experiences we perceive via our senses, like hearing something that sounds like a plane but is in fact a car. We experience that sound as an illusion but would experience it in the same manner when hearing a plane or hallucinating the sound of a plane, therefore the distinction, in terms of experience, that the physicalist draws cannot be substantiated. Thus, the Argument From Illusion is a sound argument and holds strong to these objections.

Bibliography

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2.     Barnes, W. and Broad, C., 1945. The Myth Of Sense-Data. [s.n.].

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7.     Greenberg, A.R. (1977), DEFENDING THE ARGUMENT FROM ILLUSION. The Personalist, 58: 124-130. https://doi.org/10.1111/j.1468-0114.1977.tb07489.x

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9.     Putnam, H. (1994) "Sense, Nonsense and the Senses: An Inquiry into the Powers of the Human Mind" The Dewey Lectures 1994, The Journal of PhilosophY XCI, no. 9, 472.

10.   Reynolds, S., (2000). The Argument from Illusion. Nous, 34(4), pp.604-621.

11.   Smith, David Woodruff, 2018 "Phenomenology", The Stanford Encyclopedia of Philosophy (Summer 2018 Edition), Edward N. Zalta (ed.), URL = <https://plato.stanford.edu/archives/sum2018/entries/phenomenology/>.

12.   Speaks, J., 2006. The Argument From Illusion & Hallucination. [online] Www3.nd.edu. Available at: <https://www3.nd.edu/~jspeaks/courses/mcgill/515/argument-from-illusion-2.html>.

Works Consulted

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14.   Hackett P.M.W. (2016) Theorizing Perception. In: Psychology and Philosophy of Abstract Art. Palgrave Pivot, London. https://doi.org/10.1057/978-1-137-48332-4_2