by David Pearce (Quora response)

If the doors of perception were cleansed every thing would appear to man as it is, Infinite.

– William Blake

1. You don’t perceive the environment. There is no public world. Instead, your local environment partially selects your brain states, some of which are experienced as your external surroundings. Mind-independent reality is a speculative metaphysical inference (sadly a strong one, IMO). Contra William Blake (and Aldous Huxley), there are no see-through doors of perception in need of a good wash, just cranial prisons.

2. Whether you are awake or dreaming, your world-simulation is populated by zombies. When you are awake, these zombies are the avatars of sentient beings, but the imposters loom larger than their hypothetical real-world counterparts.

3. Your egocentric world-simulation resembles a grotesque cartoon. Within the cartoon, you are the hub of reality, the most important being in the universe, followed by your close genetic relatives, lovers, friends and allies. On theoretical grounds, you may wonder if this fitness-enhancing hallucination can be trusted. After all, trillions of other sentient beings apparently share an analogous illusion. In practice, the idea of your playing a humble role in the great scheme of things can be hard to take seriously, unless the hub of the universe is psychologically depressed. Wikipedia’s List of Messiah Claimants could be enlarged.

4. Perceptual direct realism spawns a “magical” theory of reference. If direct realism is delusional, then what is the mysterious relationship between thought-episodes internal to your world-simulation and the external world? (cf. What is the current state of affairs in philosophy concerning the symbol grounding problem?).

5. A realistic interpretation of the formalism of quantum physics confirms that not just the Lockean “secondary” properties of material objects are mind-dependent, but also their “primary” properties (cf. Primary/secondary quality distinction). Shades of Bishop Berkeley? (“Esse est percipi” – “to be is to be perceived”) Kant? Not exactly, but classical physics and Copenhagen-style positivism alike are false theories of reality.

6. According to “no-collapse” quantum mechanics (Everett), you have no unique future, and no unique past. You are not the same person as your countless ancestral namesakes nor the countless folk who wake up tomorrow with an approximation of your memories (cf. Was Parfit correct about consciousness and how we’re not the same person that we were when we were born?).

7. You experience the illusion of embodiment. “In-the-body” hallucinations in biological minds pervade the animal kingdom. As out-of-body experiences on dissociative anaesthetics like ketamine reveal, physical bodies as normally conceived are cross-modally-matched illusions generated by the CNS. Or alternatively, dualism is true. Actually, not everyone has the chronic illusion of embodiment. People with negative autoscopy can stare into a virtual mirror in their phenomenal world-simulation and not see themselves. For evolutionary reasons, negative autoscopy is rare.

8. You experience the illusion of four-dimensional space-time, not high-dimensional Hilbert space. This idea is more controversial. Hilbert space is a generalisation of ordinary Euclidian space to an intuitively huge number of dimensions – conventionally infinite, though the holographic entropy bound suggests the dimensionality of what naïve realists call the observable universe is finite. Quantum mechanics may be understood via the mathematical structure of Hilbert space (cf. Nothing happens in the Universe of the Everett Interpretation). Typically, Hilbert space is treated instrumentally as a mere mathematical abstraction, even by Everettians. As David Wallace, a critic, puts it: “Very few people are willing to defend Hilbert-space realism in print.” In the interests of mental health, such self-censorship may be wise.

9. Experienced psychonauts would echo William James, “…our normal waking consciousness, rational consciousness as we call it, is but one special type of consciousness, whilst all about it, parted from it by the flimsiest of screens, there lie potential forms of consciousness entirely different.” Quite so. Our posthuman successors may regard everyday Darwinian consciousness as delusive in ways that transcend the expressive power of a human conceptual scheme.

10. We do not understand reality. Any account of our misperceptions must pass over the unknown unknowns. I fear we’re missing not only details, but the key to the plot.