Is Visual Perception Really a Nonstop Hallucination? A Plea for Conceptual Revision

Anyone who has taken Philosophy of Mind 101 will be familiar with the following claim: “We’re hallucinating reality all the time”. In this post, I will critically examine whether this statement should be taken as literally true. My intuition is that such claims are over-extended metaphors, and the true nature of visual perception is more complicated.

The popularity of the Matrix has provided a common conceptual framework to make sense of what philosophers and vision scientists have been claiming for many years e.g. Helmholtz’s claim that perception is a “unconscious inference”. The original philosophical motivation can be traced to Descartes’ musings about whether we could ever distinguish reality from a dream. Nowadays, vision scientists frame these ideas in terms of vision being “representational”.

But is it true? The argument is prima facie convincing. Start with the phenomenon of visual illusions or visual hallucinations. For example, in Charles Bonnet Syndrome (CBS) people have “complex” visual hallucinations wherein people and objects are hallucinated wholesale in dazzling detail. These fascinating cases clearly  demonstrate the brain is able to “represent” or “generate” non-existent objects in full phenomenological detail. But here’s the crucial move: if the brain can generate complex visual hallucinations, is it possible that ALL perception is a complex visual hallucination?

But as with all questions of possibility, we should be skeptical of any argument that jumps from possibility to actuality. Sure, it seems possible that ALL perception is a hallucination, but are we forced to make this conclusion on the basis of knowing that complex visual hallucinations are possible? Not at all!

I’d like to suggest a different metaphor for understanding the relation between hallucinations and normal perception that preserves their essential difference rather than collapsing them into a single, continuous category. Instead of thinking the existence of hallucinations forces us to think we are in the Matrix, I think it’s more useful to think of hallucinations as akin to augmented reality.


The idea is fairly straightforward: hallucinations such as CBS are analogous to the augmented “over-lay” in the above picture. The basic idea is that there is a more-or-less continuous stream of “veridical” perception underlying our basic animal perception and that complex hallucinations such as CBS are “projected upon” that stream just as an augmented reality HUB projects upon normal perception.

I think the AR metaphor for perception is more plausible than the wholesale Matrix hypothesis. My reasoning is grounded by an evolutionary thought experiment. Suppose for the sake of argument that the Matrix metaphor is correct and that ALL perception is a hallucination. Presumably, the brain is responsible for generating these representations. A further assumption is that more-or-less all mammalian brains have a similar hallucination generation capacity. But how did such a capacity evolve over time? Take the earliest mammalian ancestor who lived “fully” in the Matrix of their brain. How did their parent’s brain work? Was their perception only 99% a hallucination? And their ancestors’ perception 98% hallucinatory? And so on.

As we imagine the slow evolution of Matrix-style perception, we are faced with a Sorites paradox of sorts. As nervous systems get simpler and simpler it becomes implausible that nervous systems composed of only several hundred neurons are generating a completely hallucinatory inner-model. The neurons are more likely acting as a kind of complex “mediation” between stimulus and response rather than a representational medium.

But if we start going forward in evolutionary time and nervous systems get more and more complicated, it seems wrong to me to think that the brain ever “gets rid of” that underlying non-representational form of perception. Rather, the brain “adds” onto that basic veridical perception. But at no point will the nervous system switch from 50/50 veridical-hallucinatory to 100% hallucinatory such that we become fully immersed in the Matrix. Like augmented reality, the most evolutionary recent brain developments like the neocortex “overlay” more basic forms of perception.We might think of hallucinations like CBS as neocortical memory-patterns that are projected upon the real-time dynamic stream of veridical perception.

Obviously this post represents a very rough-and-ready formulation of an alternative to the standard Matrix metaphor and will need much further development. But on the other hand, I am skeptical that the Matrix metaphor has ever been rigorously developed past the level of intuitive metaphor. It’s even possible that we can never move beyond metaphor in dealing with the most unknown and esoteric psychological phenomena. And if this is the case, we have a real imperative to reexamine popular metaphors such as the Matrix and replace them with new ones.



Filed under Consciousness, Philosophy, Psychology

2 responses to “Is Visual Perception Really a Nonstop Hallucination? A Plea for Conceptual Revision

  1. Physics based on brain

    Great post! I am going to end up reading most of your blog. You should read the book
    It talks about how reality is actively generated by the brain. Its written by a neuroscientist who studies time perception among other things.

    But I understand your arguments and you do make a good point which even I have thought about. My argument is that we have to start from the information we have in the present and work backwards. And this information is our brains. So I argue that we can understand more about our universe by decoding our brains. We can also argue that not all reality is generated by our brains because our vision is only limited to 1% of the electromagnetic spectrum. So there must be a balance between the two philosophies or maybe there is more to all of our brains – because sensing the other 99% of the electromagnetic spectrum is also done by our perception! If not directly through our brains then indirectly through the instruments (which sense the other 99%) which is in turn perceived by our brains.

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