Neuroscience & Mind Icon Neuroscience & Mind

Do Perceptions Happen in Your Brain?


I have pointed out that many ordinary concepts in materialist neuroscience don’t hold up to scrutiny. You don’t store memories in your brain — you can’t store memories in your brain. Your mind isn’t a computer — in a very real sense it is anything but a computer. Your intellect and will are immaterial powers — they cannot be instantiated in matter at all.

So here’s a question: Are there any other conventional materialist interpretations of neuroscience that are logically incoherent? Consider the belief that “perceptions happen in the brain.”

First a little background. In the materialist view, there are two aspects to objects of perception: primary qualities and secondary qualities. Primary qualities, from the materialist perspective, are objective, and represent mathematically quantifiable properties such as mass, weight, dimension, location, and velocity. Secondary qualities are subjective, and represent qualities that are not crudely quantifiable but instead are experienced, such as color, taste, feel, smell, etc. Nowadays, primary qualities are thought of as the ordinary physical properties of an object. Secondary qualities are thought of as qualia — the subjective experience of things.

In the materialist view, when you perceive an object, what really happens is that the primary qualities of the object stimulate a sense organ of yours (a touch receptor, or a retinal cell, or a cochlear cell, etc.). The stimulus is transmitted to your brain, and it is in your brain that the stimulus acquires its secondary qualities — pain, or vision, or hearing. The pain or color or harmony isn’t really in the object perceived. It’s in your brain.

You don’t really perceive the object in your environment directly; you perceive the secondary qualities that are evoked in our brain by the transmission of the nerve stimulus, which is excited by the primary qualities. The object itself — the injured finger, the tree that you see, the music that you hear — are merely physical things in the external world that don’t have any subjective qualities in them at all. The subjectivity is in you — in you brain, and your nervous system serves only to transmit the objective signal to your brain so you can have a subjective experience.

This primary/secondary quality distinction dates to Democritus and the atomists in ancient Greece (the inference to the brain as the terminus of perception is more modern), and the full modern iteration began with the early modern philosophers, particularly Locke. Aristotelians and Thomists have always considered these primary/secondary quality distinctions misguided, for reasons that will be apparent.

So let’s take a look at the materialist concept of perception as expressed in modern neuroscience. Consider that a pin pricks your finger. By the materialist paradigm, the primary qualities of the pin (its mass, location, and sharp shape) stimulate a nerve ending in your finger, which transmits an action potential to your cortex. At your cortex, the activation of the cortical neurons results in your perception of the secondary quality of the pinprick — the pain in your finger.

Is this how it really happens? Consider this experiment. I wish to empirically demonstrate the arrival of the stimulus in my brain — the arrival that corresponds to my subjective awareness of the pain. So I hook myself up to an EEG to record my brain waves. Sure enough, when my finger is pricked, a brain wave spike occurs in my somatosensory cortex — I’ve confirmed where my conscious awareness of the secondary qualities of the pain occurs!

But there’s a problem. In the materialist paradigm, all of the conscious experience of all sensory inputs occurs in the brain, including vision. So when I observe the arrival of the stimulus on the EEG machine that corresponds to my brain wave, that stimulus blip itself is a primary quality, and it is only experienced by me when the image of the stimulus arrives in my brain — in my visual cortex. So in my experiment, when I observe my pain event in my brain, the event actually occurs in my visual cortex (corresponding to my observation of the stimulus), not in my somatosensory cortex. There is no reason to privilege the somatosensory cortex over the peripheral sensory receptor as the site of my experience, so any effort I make to observe this event experimentally will put the event in my visual cortex, not my somatosensory cortex.

It gets worse. If I decide to experiment further and observe the event in my visual cortex, I must have another observation in my visual cortex at which the pain perception is actually located, rather than in the first visual cortex location or in my somatosensory cortex. My materialistic interpretation of my perception has led me to infinite regress! Aargh!

So, materialistically exasperated, I ask my fellow neuroscientist Joe: “Joe, I’ve got myself a nasty infinite regress. I claim that my sensory cortex is the site of my perception of pain, but if I observe my sensory cortex reacting to pain, then I have to place the event in my visual cortex, which is now the site of my pain! Joe — could you do me a favor and test my brain, to objectively demonstrate the pain event in my brain, so I’m not stuck in infinite regress?”

So Joe helps me out. He does a variety of experiments (EEG, fMRI, direct recordings of electrodes on my brain) to document the arrival of the stimulus in my sensory cortex and thus to locate my perception of pain.

“Well, Mike, I’ve located your site of pain perception.”

“Where is it, Joe?”

“It’s in my brain!” says Joe. “You see,” said Joe, “when you have a perception of pain and your cortex activates, I observe that happening with all of my tests. But if I am faithful to the materialist interpretation of perception, I then have to affirm that the events that appear to happen in your brain actually happen in my brain. You feel pain in my brain!”


The difficulty with the materialist understanding of perception — that primary qualities stimulate sensory organs and that perception only occurs in the brain when the secondary subjective qualities are conjured in the brain — is that there is no reason to privilege the primary qualities of the signal in the brain itself, and any effort to observe the brain event necessarily shifts the actual perception to another brain event. Materialist perception can’t be observed, if one is to be logically consistent, without infinite regress.

The materialist explanation for perception — the explanation extant in most journals and textbooks of neuroscience — is self-refuting gibberish. So where does perception occur, if not in your brain?

The answer is simple. Perception is a wholly material thing — it does have location. When you perceive a pinprick on your finger, your perception of the pinprick occurs on your finger where it is pricked. This understanding has remarkable, but undeniable, consequences. When you perceive music from your radio, your perception of the music occurs at your radio. When you perceive a tree in your yard, your perception of the tree occurs at the tree. When you perceive the moon, your perception of the moon occurs at the moon. Perceptions occur at the object perceived, regardless of distance, regardless of location. It seems bizarre, but it is logically sound and, when you think it out a bit, it is plainly true.

The alternative — that perception occurs in your brain — is logical nonsense, because the effort to observe the occurrence of the perception in your brain demonstrates (by the same reasoning) that the perception is not in your brain but in the brain of the observer, ad infinitum.

This simple logic dates to Aristotle, who made no fundamental ontological distinction between primary and secondary qualities. He noted that perception entails the mind grasping the form (he called it the “sensible species”) of the object at the location of the object. He was a bit astonished himself at this fact. He commented that the mind is not a passive recipient of perceptions — it actively grasps the sensible properties of objects and it does so externally — at the objects perceived.

Remarkably, Aristotle’s simple rule of perception is consistent with <href=”#experiment”>experiment. The sensory experiments of Benjamin Libet, a neuroscientist at U.C. San Francisco in the mid 20th century, demonstrated that a subject perceives a sensory stimulus on the skin at the moment the skin is touched, before the stimulus reaches the brain and before full deliberative consciousness occurs. Libet was flabbergasted by this result and hypothesized that “the subjective timing of the experience is (automatically) referred backwards in time.” Yet Aristotle offered a much simpler and logically coherent explanation — the stimulus on the skin is perceived on the skin, not in the brain. Perception occurs at the location of the stimulus, not in the brain.</href=”#experiment”>

Only your perception of your brain would genuinely be “in your brain,” just as your perception of the pain in your finger is in your finger, and the perception of the tree in your yard is in your yard. Your mind is not bound by location. Wherever the object is that you perceive, the location of the object is where you perceive it. Your mind grasps — becomes one with — the form of the object, at the object, yet your mind remains itself. The mind, a power of the soul, is, in Aristotle’s terms, the form of forms. The mind is a form capable of grasping other forms and perceiving them, while remaining itself. It is not constrained by location.

Aristotle said it quite beautifully: “the soul is in a way all existing things…” (De Anima iii 8).

There are several excellent references for this basic fact of perception. Aristotle’s De Anima (particularly books II and III) is one of his more accessible works. Mortimer Adler’s Ten Philosophical Mistakes is invaluable — this fact of perception is discussed in the first two chapters. Edwin Burtt, in his superb The Metaphysical Foundations of Modern Physical Science, discusses this in detail in his concluding chapter. M.R. Bennett and P.M.S. Hacker discuss these philosophical issues exhaustively in several of their works. And Ed Feser is indispensible for an introduction to the Aristotelian/Thomist understanding of nature.

Image credit: Chepko Danil / Dollar Photo Club.

Michael Egnor

Senior Fellow, Center for Natural & Artificial Intelligence
Michael R. Egnor, MD, is a Professor of Neurosurgery and Pediatrics at State University of New York, Stony Brook, has served as the Director of Pediatric Neurosurgery, and award-winning brain surgeon. He was named one of New York’s best doctors by the New York Magazine in 2005. He received his medical education at Columbia University College of Physicians and Surgeons and completed his residency at Jackson Memorial Hospital. His research on hydrocephalus has been published in journals including Journal of Neurosurgery, Pediatrics, and Cerebrospinal Fluid Research. He is on the Scientific Advisory Board of the Hydrocephalus Association in the United States and has lectured extensively throughout the United States and Europe.