Does hallucinating involve perceiving?

This paper benefitted from the feedback of my dissertation committee members, Otavio Bueno, Elijah Chudnoff, Simon Evnine, and Susanna Schellenberg, all of whom helped shape my view. The thorough comments of an anonymous reviewer at Philosophical Studies also helped clarify the paper’s argument and organization. Finally, the members of New York University Abu Dhabi’s Normativity conference in February 2016, and the members of the American University of Beirut’s philosophy department also contributed with their comments to my presentation on part of this paper.


A natural starting point for theories of perceptual states is ordinary perception, in which a subject is successfully related to her mind-independent surroundings. Correspondingly, the simplest theory of perceptual states models all such states on perception. Typically, this simple, common-factor relational view of perceptual states has received a perfunctory dismissal on the grounds that hallucinations are nonperceptual. But I argue that the nonperceptual view of hallucinations has been accepted too quickly. I consider three observations thought to support the view, and argue that all three are dealt with equally well by an alternative view, illusionism, on which hallucinations do involve perception. Since this is so, adopting a common-factor relational view of all perceptual states remains a tenable option.

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  1. 1.

    In what follow I use ‘perceptual state’ rather than ‘perceptual experience’. A perceptual state is one part (the perceptual part) of a subject’s total experiential state. I do this as a matter of convention, as I think neither perceptual state or perceptual experience are clearly defined in everyday use.

  2. 2.

    This is an overally brief characterization of relationalism. Much more can be said, and has been said, to explain what the distinctive relation of perceptual contact amounts to. For more, see e.g. Campbell (2002), Fish (2009), Brewer (2011), and Genone (2014).

  3. 3.

    ‘Relationalism’ is typically used to describe a view of veridical perceptual states, or states of perception. I use the term in a broader sense throughout (unless otherwise stated), applying it to all perceptual states, and not just veridical ones.

  4. 4.

    Here I characterize relationalism as involving the identification of perceptual states with states of perceptual contact with worldly objects. But weaker construals of the view are possible. For instance, one can take perceptual states to constitutively involve perceptual contact with objects without being identical to such contact. I adopt this construal for ease of exposition, nothing in what follows rests specifically on accepting the stronger identity commitment.

  5. 5.

    For instance, see Fish (2009), Brewer (2011), and Genone (2014).

  6. 6.

    Throughout I use ‘perception of x’ and ‘perceptual contact with x’ interchangeably. More generally, as I understand it, relationalism is the view that all perceptual states involve perception. .

  7. 7.

    This position is similar to Fish’s (2009), although Fish does not require that the obfuscating state be coupled with perceiving.

  8. 8.

    I say more about the connection between disjunctivism and relationalism, and representationalism and common factor views below.

  9. 9.

    For more, see e.g. Pautz (2010) and Haddock and MacPherson (2011).

  10. 10.

    For instance, see Martin (2006) and Brewer (2011).

  11. 11.

    I add ‘sensory’ to distinguish the type of phenomenal character typically associated with perceptual states from other types of phenomenal character, such as cognitive phenomenal character. In the remainder of the essay, I will usually omit ‘sensory’, since I do not discuss other types of phenomenal character.

  12. 12.

    For instance, both Descartes’ evil demon case (which is a case of hallucination) and Hume’s argument from illusion were thought to establish that we do not have direct experience of the mind-independent world.

  13. 13.

    One can also accept other types of monism. For instance, an anonymous reviewer has noted that illusions and hallucinations look identical from the contemporary viewpoint if all one is concerned with is perceptual contact with properties.

  14. 14.

     I discuss some of these in my dissertation, El Ali (2014).

  15. 15.

    For more on this, see Campbell (2002), Brewer (2011) and Genone (2014).

  16. 16.

    For a detailed discussion of the relationship between perceptual states, objects, appearances, and perceptual error, see Genone (2014). I also provide a brief discussion of the relationship between appearances, phenomenal character, and perceptual states in the following section.

  17. 17.

    Though I focus on vision, this also carries over to other senses. For instance, in auditory stereo illusions, the sound appear to move around even though its source does not. A readily available online example is the Barbershop illusion.

  18. 18.

    Michael Huemer, for instance, has suggested this in discussion.

  19. 19.

    The Hurwitz Singularity installation was brought to my attention in a discussion with Alex Byrne.

  20. 20.

    For some examples of the conditions under which real hallucinations occur, see Sacks (2012). For a more technical discussion, see Ffytche (2013).

  21. 21.

    Smith (2002), Fish (2009), Genone (2014), and Raleigh (2014).

  22. 22.

    Fish (2009 p. 93).

  23. 23.

    Fish (2009, p. 93).

  24. 24.

    Genone (2014 p. 360) (emphasis mine).

  25. 25.

    Raleigh (2014), for instance, calls causally matching cases perfect hallucinations.

  26. 26.

    Soteriou (2016).

  27. 27.

    Fish understands pure hallucinations as he does because on his view relationalism involves identifying a state’s phenomenal character with the property of acquainting the subject with a given object’s presentational character.

  28. 28.

    For instance, see Genone (2014) pp. 343–344.

  29. 29.

    It would be odd to deny this because perceptual contact involves objects appearing some way to the perceiver, and so denying the involvement of perceptual contact in a state’s sensory phenomenal character involves denying that objects appearing some way constitutes at least a part of a state’s phenomenal character.

  30. 30.

    For instance, see Schellenberg (2016), who denies that the sensory character of perceptual states is (even partly) constituted by the particulars perceived (though particulars are constitutive of perceptual states in other ways).

  31. 31.

    Examples of interactions between different senses abound in the literature. Some cases involve interference between inputs from two functioning sense modalities e.g. the McGurk effect, the ventriloquist effect, and the sound induced flash illusion, amongst others. Others, like some cases of synesthesia, involve inputs from one modality being processed in two modalities (e.g. an object heard might be experienced auditorily and visually). Finally, some cases involve the stimulation of one sense modality generating and experience in another. For instance, vestibular stimulation causes amputees to hallucinate phantom limbs, even when they have not experienced phantom limbs before (Lopez et al. 2012). Another study (Dieter et al. 2014) shows that at least half of its participants reported sensory awareness of their bodies, when in full darkness, plausibly because of crossmodal interaction.

  32. 32.

    An argument of this sort is proposed and defended by Raleigh (2014).

  33. 33.

    Watzl (2010, p. 243).

  34. 34.

    Davis et al. (1976).

  35. 35.

    For a detailed discussion and extended defense of perceiving absences, see Sorensen (2008).

  36. 36.

    This sort of calibration is apparent if we think about a case of walking into a regularly lit room from the sunlit outdoors. It usually takes our eyes a few seconds to adjust our perception of the room, and prior to that the room looks more dimly lit than it is.

  37. 37.

    For instance, see Wackermann et al. (2008)

  38. 38.

    Here I am bracketing the fact that Ocular’s previous perceptual states might somehow inform it visually e.g. via memory, since we can conceive a case in which Ocular is unnaturally born without a visual system.

  39. 39.

    In my view, Fish’s (2009) account of pure hallucinations reduces them to what are more aptly called delusions. Delusions are cognitive rather than perceptual (like hallucinations), though they certainly affect the way we understand and conceptualize our perceptual world.


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Ali, R. Does hallucinating involve perceiving?. Philos Stud 175, 601–627 (2018).

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  • Hallucinations
  • Perception
  • Misperception
  • Illusionism
  • Relationalism
  • Naïve realism
  • Common-factor
  • Philosophy of perception
  • Philosophy of mind