The Illusion of Perception (Saññā) – It Is Scientific Consensus

• The external world consists of molecules and compounds; our perceptual reality ascribes qualities such as bitter, salty, and umami, rendering eating a subjective experience far removed from the chemical facts.
• Many animals prefer the taste of certain things that would not even be considered food. For example, pigs eat rotten foods or even feces; that means they like the taste (and also smell) of them! Their bodies are formed to be able to extract nutrition from those things, even though we will get sick if we eat them. (My comment: Further details in the next post on ‘Different Species Have Different Types of Perceptions (Saññā).’)

7. Smell follows a similar pattern. Odors don’t exist as we perceive them; they’re volatile molecules floating in the air that bind to receptors in the nose. These trigger signals to the brain, which constructs the smell, whether it’s roses or coffee.

• Evidence comes from anosmia, the loss of smell, which is often observed in conditions such as COVID-19. The molecules are still there, but without brain processing, there’s no odor.
• Phantosmia, in which individuals smell things that aren’t present (e.g., burning toast during a migraine), demonstrates that smells can arise purely from brain activity, without external molecules.
• Cultural differences highlight subjectivity: what smells pleasant to one person (such as durian) might be repulsive to another. The molecules are identical, but perceptions differ across individuals. In blind smell tests, people often misidentify familiar scents when labels are removed, revealing how context and expectation shape the experience.
• The brain can even blend smells in unexpected ways, as in wine tasting, where aromas combine into complex flavors not present in isolation. The external reality is just molecules; smell is the mind’s creative interpretation.
• See Science of the Senses I Season 1 I Episode 4 

8. Pain feels the most “real” because it’s tied to the body, yet it’s equally a mental construct.

• Pain arises when nociceptors detect potential harm, signal the brain, and the brain creates the sensation. Without the brain, there’s no pain—just tissue damage. Some people don’t feel physical pain (which is a kamma vipāka, because they may bleed to death; see “Why Some People Don’t Feel Pain“)
• Phantom limb pain is a classic example: amputees feel agony in missing limbs. There’s no injured tissue, yet the pain is real because the brain generates it. Hypnosis or placebos can reduce pain without changing the injury, showing it’s perceptual. Chronic pain conditions, where pain persists long after healing, illustrate this disconnect. Soldiers in battle sometimes don’t feel wounds until later—the same damage, but context alters perception. Anesthesia blocks pain signals, but the injury remains; the mind simply doesn’t register it.
• Some people, due to rare conditions like congenital insensitivity to pain, never feel pain despite injuries. The external stimuli are there, but perception is absent. Pain isn’t in the body—it’s the mind’s alarm system, often unreliable.
• See “History of Pain: A Brief Overview of the 17th and 18th Centuries.”

• Ancient Times (4th Century BCE): Aristotle, in works such as “De Anima,” held that qualities like color and taste are inherent in objects and are perceived directly by the soul. This object-centered view dominated for millennia. See “Primary and Secondary Qualities in Early Modern Philosophy.” 
• 17th Century: The Dawn of Distinction: In 1623, Galileo Galilei argued in his book “The Assayer” that tastes, odors, colors, and sounds are not in external objects but reside in consciousness. He stated that without a perceiver, these qualities wouldn’t exist, marking an early shift to subjective perception.
• René Descartes, in the 1640s, explored pain in “Meditations on First Philosophy” and “Principles of Philosophy,” noting phantom limb pain as evidence that pain is a perception of the soul or mind, not the body itself. See “History of Pain: A Brief Overview of the 17th and 18th Centuries.”
• Late 17th Century: Primary vs. Secondary Qualities: John Locke, in his 1690 “An Essay Concerning Human Understanding,” formalized the distinction. Primary qualities (shape, size, motion) exist in objects; secondary qualities (color, taste, smell, sound) are powers in objects to produce ideas in the mind. This framework influenced centuries of thought. See “John Locke’s Empiricism: Why We Are All Tabula Rasas (Blank Slates).”
• 18th Century: Deepening Subjectivism: George Berkeley, in “A Treatise Concerning the Principles of Human Knowledge” (1710), extended this to argue that all qualities are perceptions—”to be is to be perceived.” David Hume, in “A Treatise of Human Nature” (1739), reinforced that colors, sounds, tastes, and smells are merely perceptions, without independent existence. See Chapter 10 in “Primary and Secondary Qualities: The Historical and Ongoing Debate,” edited by Lawrence Nolan (2011).
• Thomas Reid, in the late 1700s, critiqued and refined the primary-secondary distinction in “Essays on the Intellectual Powers of Man” (1785), emphasizing that secondary qualities such as smell and taste are known only through sensation. See Chapter 11 in “Primary and Secondary Qualities: The Historical and Ongoing Debate,” edited by Lawrence Nolan (2011).
• 19th Century: Nerve-Specific Sensations: Johannes Müller, in the 1830s, through his “law of specific nerve energies,” showed that sensations depend on which nerves are stimulated, not the external cause. For example, pressure on the eye produces light sensations, proving color is nerve-dependent. Hermann von Helmholtz applied this to the perception of sound and color in his work on physiological optics (1850s-1860s). See “A Brief History of Sensation and Reward.”
• In 1965, Ronald Melzack and Patrick Wall described pain as a multidimensional experience influenced by brain gates rather than by direct input in their paper on the gate control theory. Neuroscience studies confirmed phantom pains and hallucinatory smells/sounds as brain-generated. See “Pain Theory.”
• For music, research in auditory perception, as in Hermann von Helmholtz’s works, was revisited, showing harmony as a psychological phenomenon. This timeline shows a gradual shift from viewing qualities as objective to recognizing them as mental constructs grounded in observation and argument.
• Neuroscience (late 20th Century – Present): Modern neuroscience, using tools such as fMRI and EEG, has provided concrete evidence that the brain is an active constructor of reality (My comment: more correctly, the mind is the constructor with the help of the brain). Studies consistently show that perception involves extensive neural processing, pattern recognition, and predictive modeling, confirming that we interact not with the raw world, but with a highly edited neural simulation.

Implications: Bridging Perceptual and Fundamental Reality

10. The gap between fundamental physical reality and perceptual reality is not a philosophical abstraction but a fact demonstrated through scientific evidence, optical illusions, and neurological conditions.

• Understanding that our senses create a subjective world has profound implications. It explains why witnesses disagree on colors in accidents or why food tastes different to each person. It highlights the gap between what we experience and what’s truly out there—waves, molecules, vibrations—reminding us that reality is filtered through the mind.
• Yet, this doesn’t diminish our experiences; it enriches them by revealing the brain’s creative power. Most people go through life assuming their perceptions mirror the world precisely, but grasping this fact fosters humility and curiosity about the unseen fundamental reality.
• My Comment: We are born human with a built-in ”illusion of perception’ (viparīta, or distorted saññā). Those perceptions should not be disregarded, because they are, in many cases, essential for our survival. Even an Arahant experiences it and lives with it until the death of the physical body. But an Arahant has ‘seen with wisdom’ that is a mirage (in the ultimate truth or paramattha) and thus their minds do not attach to the ‘mirages.’ This is a subtle but critical point. See #10 of “Attachment Is to Saññā, Not to Pañcakkhandha.”

References – Books

11. For further reading and viewing, here are general resources that present these facts:

• “An Essay Concerning Human Understanding” by John Locke (1690) – Classic on primary and secondary qualities.
• “The Assayer” by Galileo Galilei (1623) – Early arguments on subjective sensations.
• “A Treatise of Human Nature” by David Hume (1739) – Explores perceptions without external existence.
• “Incognito: The Secret Lives of the Brain“ by David Eagleman (2012): This accessible book explores how the vast majority of our brain’s operations are unconscious, demonstrating that our conscious perception is merely the tip of the iceberg of neural activity. Eagleman clearly outlines the brain’s role in constructing reality.

Videos and Documentaries:

Overall Perception: The Reality of Reality: A Tale of Five Senses

• My Comment: Scientists in the video above attribute differences in human and animal perceptions to evolution. However, the Buddha attributed them to the different ways in which species arise, depending on the types of cultivated gati. This aspect of Paticca Samuppada requires contemplation. See #13 below.

Simple explanation of color as perception: How we see color – Colm Kelleher

Explores how light isn’t color: NOVA | Your Brain: Perception Deception | Season 50 | Episode 9 | PBS

Details on smell perception: Harold McGee | Nose Dive: A Field Guide to the World’s Smells | Talks at Google

Taste and smell as brain processes: Taste & Smell: Crash Course Anatomy & Physiology #16

History and facts of color perception: Adam Rogers | Full Spectrum: The Science of Color and Modern Human Perception

Summary

12. The external world, the one existing independently of human observation, is fundamentally composed of matter, energy, physical forces, and properties described by physics. Our human experience of this world—full of vibrant colors, rich sounds, strong flavors, and the very sensation of pain—is not a direct mirroring of these physical properties.

• Sound: In the external world, sound is variations in air pressure—compressions and rarefactions of molecules traveling as waves. In our minds, these become the subjective experience of music, voices, or noise.
• Taste and Smell: The external reality involves chemical compounds interacting with receptors. The brain translates these interactions into the perception of “sweet,” “savory,” “acrid,” or “fragrant.”
• Touch and Pain: Physical pressure, temperature changes, or tissue damage activate nerve endings. The sensations of “smoothness,” “cold,” or “pain” are the brain’s interpretation of these signals. Some individuals experience congenital insensitivity to pain (CIP), a condition in which the physical mechanisms of nerve signaling are intact but the brain fails to produce the sensation of pain, further demonstrating its nature as a constructed perception.
• The shared fact across all these phenomena is that the perceived qualities—philosophers use the word qualia—exist only within the boundaries of the mind.

Relevance to Buddha’s Teachings 

• However, it has enormous implications if rebirth is true. We commit ALL akusala kamma based on attachment to ‘mind-made pleasures’ generated via the illusion of perception. The rebirth process is fueled by those akusala kamma!
• We would not attach to sights, sounds, tastes, smells, and touches unless they provide a ‘pleasure sensation.’ Think about that carefully. A colorless world would be dull and void of joy; see “Colors Are Mind-Made (Due to Kāma Saññā).” Would we crave eating food if it didn’t have any taste? Nature is the ‘greatest magic show,’ and it is maintained via Paṭicca Samuppāda. See “Saññā – Hidden Aspect of Paṭicca Samuppāda” and “Paṭicca Samuppāda Creates the External World, Too!” Understanding these posts requires a decent knowledge of Paṭicca Samuppāda.
• By the way, those ‘pleasure sensations’ are ‘real’ in the sense that our bodies (and the environment) arise to provide them. Even an Arahant would taste sugar as sweet. Even though Paṭicca Samuppāda generates ‘illusive perceptions’ that keep us bound to the rebirth process, they also help the survival of all living beings. In addition, akusala kamma lead to physical and mental suffering. Paṭicca Samuppāda is a ‘neutral complex process’ that brings about rebirths according to cravings and their side effects like anger and jealousy; see Paṭicca Samuppāda – “Pati+ichcha”+“Sama+uppāda”. Further details in the next post on “Different Species Have Different Types of Perceptions (Saññā).”
• We cannot lose our cravings by sheer willpower. The only way to lose cravings is to fully comprehend the fact that Nature is the ‘greatest magic show.’ Also see “Sandiṭṭhiko – What Does It Mean?“
• Thus, the ‘illusion of perception’ (viparīta, or distorted, saññā) plays a critical role in keeping us bound to the suffering-filled cycle of rebirth. See “Fooled by Distorted Saññā (Sañjānāti) – Origin of Attachment (Taṇhā).”