Hallucination as Public and Private

the first in a triptych of posts on hallucination

I’ve hallucinated music since at least my early teens, maybe earlier. (Voices came much later.) I didn’t figure out that ‘hallucinating music’ is a distinct kind of experience—a sound ‘in the world’ that is not available to other people—until my late teens.

These days, I’m so used to hearing ‘music that isn’t there’ that it doesn’t phase me (which is not to say that it isn’t sometimes very distracting; but then again, sometimes it is very pleasant—we take the good with the bad, and that’s called ‘living’). Most of the time, it is clear whether music is real or hallucinated, and even when it is unclear, the ambiguity is almost never disturbing. Sometimes I even hum or whistle along so that my wife can hear it—she calls it the ‘soundtrack’ to my life.

Voices are a different matter, perhaps because they started much later in life, perhaps because they are often the voices of familiar people, or perhaps because unlike music, voices can so readily demand one’s attention, either directly (“Hey! Listen to me!”) or because it can be difficult to ignore words, regardless of their origin.

A few months ago, I decided to try to understand these points better, motivated by reading Justin Garson’s fascinating book Madness: A Philosophical Exploration. In that book, he explores (with many historical examples) a way of thinking about ‘madness’ as a kind of ‘strategy’, as the mind ‘doing what it is, in some sense, supposed to be doing’, even if the experience of it can be disturbing and harmful. The analogy that I’ve been using for myself—stolen from Plato’s dialogue The Phaedrus (251c)—is that madness could be like a baby’s teething, an experience that serves a useful purpose even if it can also be unpleasant. (I don’t in any way mean to diminish the serious, potentially deadly, consequences of madness. Garson doesn’t either.)

What if hallucination is ‘madness as strategy’? This question prompted me to read more. The next three posts will be a brief, selective, and idiosyncratic reaction to what I read, in both philosophy (this post) and psychiatry (next post), followed (third post in this triptych) by my own crazy speculation that hallucination and memory may be very similar.

So for today: The philosophers. I turned to philosophical books such as Hallucination: Philosophy and Psychology, and Perception, Hallucination, and Illusion, and from there to hosts of professional articles from the past ten years or so. (They are easy to find once you figure out how to avoid the avalanche of articles about ‘hallucination in AI’.) Initially, I forgot how to be a philosopher and kept asking “What on earth are these people talking about?” My mistake was in thinking that they are writing about actual hallucination. My mistake.

The philosophers do not seem to be discussing any actual experiences that any actual people have. (They do sometimes seem to be talking about real examples, so perhaps they share some of the blame for my mistake.) Instead, they are exploring—or at least, are apparently motivated by—a skeptical challenge: If people can hallucinate, then on what grounds can one ever be confident that one’s perception corresponds to the real world? You could be hallucinating right now. How are we to understand the difference (if any) between accurate perception and hallucination?

Answering this question will not, by itself, ease anybody’s philosophical angst about skepticism (roughly, the view that maybe nobody can know anything), an angst that I have never been able to make myself feel. (I’m comfortable with the possibility that there is a great and indeterminate gulf between ‘the world as reported by perception’ and and ‘the world as it really is,’ whatever the latter is supposed to mean.) The point, for these philosophers, at this stage of the discussion, is just to establish whether some distinction between hallucination and perception provides a foundation upon which a response to skepticism might be erected.

One side (let’s call them the ‘Unifiers’) says ‘no’: “Hallucinations and perceptions are unified as psychological experiences—the only difference between them is that in hallucination there is no external object causing the experience. The ‘Dividers’ say ‘yes’: “Hallucination differs from perception not only in lacking a real-world object, but also in being a different kind of mental state.” For example, in one version (expounded by William Fish in the second of the two books mentioned above), hallucination is not a perception-like experience, but the (false) belief that one is having a perception-like experience.

Positions taken in the debate do sometimes feel a bit like ‘winning by naming’ (a phrase I learned from my old mentor, talented philosopher, and all-around wonderful human being, Jeremy Butterfield). Note, for example, that no first-personal report of any kind could ever defeat Fish’s (‘disjunctivist’) position. One might say to Fish: “Sometimes I really cannot tell the difference between the experience of ‘merely hearing voices’ and the experience of hearing actual people speaking; so aren’t both of those experiences thereby ‘perception-like’?” Fish’s reply: “No, hallucinating voices is by definition believing (falsely) that one hears voices, so you would say that.”

It can be a bit frustrating, until one realizes that the target of analysis in this philosophical work is not actual hallucination. Instead, the term ‘hallucination’ names a creation of philosophical imagination, intended as a tool to explore skepticism, the nature of perception, and related topics. This realization came to me upon encountering the philosophical concept of ‘total hallucination’, in which the entirely of one’s (alleged) perceptual experience is hallucinatory. It does not seem to be (nor need to be) the name of anybody’s actual experience. (I’ve never knowingly had such an experience; nor have I heard of it from others, nor seen it reported in the psychiatric literature.)

One of the notable differences between philosophical hallucination (‘total’ or otherwise) and actual hallucination is that people who actually hallucinate are sometimes aware that they are hallucinating, at least in the sense that they are aware that others do not (or would not, if present) have the same perceptual experience. For example, I often hallucinate a particular voice when I’m driving. It sounds like somebody speaking from the back seat, but I know that it is not, and I know that when others are in the car with me, they won’t hear it.

And here is the final point: Knowledge that one’s experience is hallucinatory is part of the phenomenology of the experience. I do not mean that this knowledge cancels the perceptual character of the experience (in whatever manner it may be perceptual, which will be considered in the next post). When I hallucinate that voice in the car (always the same voice), I am generally aware that I’m hallucinating, but this awareness does not cause me to experience it as something other than an audible voice. The point is rather that a perceptual experience that one knows also to be private is its own kind of perceptual experience.

Consider, for example, this student’s report of a voice named ‘Hilda’ (quoted from p. 7 of Ynnesdal Haugen 2024):

Hilda keeps giving me wrong answers all the time. It’s so embarrassing to show the teacher the wrong answers. And I can’t tell him that they’re not my answers but her answers. He’ll think that I’m completely mad! Which I am, though, but he doesn’t have to know, does he?

This student understands that Hilda is not part of what Sofia Jeppsson (2023) calls the “Mainstream World,” and yet does not, on that account, stop hearing Hilda. Consider the possibility that the student hears both Hilda and ‘mainstream’ voices in a perceptual-like manner, but still differently. Hilda is heard as not available to others. For example, referring to Hilda publicly is in general not a good idea—it is embarrassing and weirdly isolating and even potentially dangerous. Hilda is both ‘out there’ and private, and experiencing Hilda’s voice is thus unlike hallucination as described by both Unifiers and Dividers.

Oversimplifying the matter for the moment: The Unifiers are correct that hallucination can be like perception—hallucinated voices and actual voices sound the same—while the Dividers are correct that hallucination can still be quite different from perception of the Mainstream World. The latter is the perception of something as publicly available while the former is perception of something as private.

---

References

Fish, W. 2009. Perception, Hallucination, and Illusion. Oxford: Oxford University Press.

Garson, J. 2022. Madness: A Philosophical Exploration. Oxford: Oxford University Press.

Jeppsson, S. 2023. Radical Psychotic Doubt and Epistemology. Philosophical Psychology 36(8):1482–1506.

MacPherson, F., and D. Platchias, eds. 2013. Hallucination: Philosophy and Psychology. Cambridge, MA: MIT Press.

Ynnesdal Haugen, L. 2024. Towards Validating Invalidated Knowledge: A Discourse Analysis of Firsthand Accounts of Hearing Voices. BMC Psychology 12:527.