Chapter 1   Introduction: The Priority Question Between Philosophy and Cognition

1.1   Research Questions

When, why, and how did humans begin to think philosophically? What are the cognitive preconditions for abstract thought? Why did only humans develop purely abstract thinking (such as mathematics and metaphysics) while other animals did not? These questions constitute the core intersection of epistemology and cognitive science. Conventional histories of philosophy typically begin with Thales (c. 624–546 BCE), treating the birth of philosophy as a kind of “spontaneous mutation of thought.” This paper challenges that narrative, arguing that the origins of philosophy must be traced back to the level of cognitive biology.^[1][2]

1.2   Core Hypotheses

1.2+   Defining the Core Concept: A Unified Definition of “Factual Absence”

1.3   Methodology and Paper Structure

This paper adopts a cross-disciplinary integrative approach, synthesizing evidence from evolutionary biology, cognitive neuroscience, archaeology, the history of philosophy, the history of mathematics, and anthropology. The argument unfolds along “the evolutionary ladder of cognitive capacities,” progressing level by level from the brain’s biological processes to civilization’s institutional products, demonstrating the origins, nature, and practical transformation of abstract thinking.

Chapter 2   Cognition Preceded Philosophy: Evidence from the Evolutionary Timeline

2.1   Brain Evolution and the Neural Basis of Abstract Capacity

2.1.1   The Evolutionary Connectivity of the Default Mode Network (DMN)

Two systems in the human brain — one responsible for cognitive tasks and the other for suppressing external events — were only connected in recent evolutionary history. Garin et al. (2022) demonstrated that non-human primates lack the strongly correlated activity between the medial prefrontal cortex and the posterior cingulate cortex that is a defining feature of the human default mode network.^[9] This connectivity may have facilitated the emergence of abstract thinking capacity. More critically, the DMN is simultaneously responsible for dreaming, daydreaming, and philosophical contemplation — suggesting a deep sharing of neural substrate among all three.^[10]

2.1.2   The Disproportionate Expansion of the Prefrontal Cortex

The evolutionary expansion of the human prefrontal cortex made metacognition — “thinking about thinking” — possible. In a study published in PNAS, Premack (2007) demonstrated that microscopic research on the human brain has revealed neural structures, enhanced wiring, and forms of connectivity between nerve cells not found in any other animal.^[11] This is the neural prerequisite for abstract thinking — without metacognitive capacity, reflective processing of dreams and hallucinations would be impossible.

2.2   The Evolutionary Ladder of Cognitive Capacities

Each cognitive transition strictly preceded the next level of reflective thought. Philosophy, as systematic reflection, was the last capacity to appear on this ladder.^[3][4][12]

2.3   Piaget’s Genetic Epistemology: Verification at the Individual Level

Piaget’s research in genetic epistemology demonstrates that knowledge evolves from basic sensory experience to abstract reasoning through a strict stage sequence: sensorimotor stage (ages 0–2) → preoperational stage (ages 2–7) → concrete operational stage (ages 7–11) → formal operational stage (from age 11).^[13] Philosophical thinking — performing abstract operations on abstract concepts — becomes possible only during the formal operational stage, and no one can skip the preceding three stages. This sequence of individual cognitive development recapitulates the sequence of cognitive evolution in the human species.

2.4   Embodied Cognition: Abstract Concepts Grow from Bodily Experience

In their groundbreaking work Philosophy in the Flesh (1999), Lakoff and Johnson advanced three core findings: the mind is inherently embodied; abstract thought is largely metaphorical; and most thinking is unconscious.^[14] They demonstrated that all abstract philosophical concepts — including causality, time, and morality — can be traced to origins in bodily metaphor. For example, “understanding” in Chinese is “把握” (literally “grasping”), and in English it is often expressed as “grasp” — both mapping to the action of the hand. This proves that cognitive operations preceded conceptual operations.^[15]

However, embodied cognition and the central thesis of this paper are not in competition but rather stand in an upstream-downstream relationship. Embodied experience supplies the alphabet; factual absence states alter the grammar. The snakes, flights, deaths, and lights that appear in dreams all originate from bodily experience, memory, and emotion — no one can dream of something they have never encountered in any form. Yet embodied experience in the waking state is strictly constrained by physical laws: stones cannot fly, the dead cannot speak, sounds cannot be seen. The role of factual absence states is not to supply entirely new materials but to remove the combinatorial constraints on those materials — allowing stones to fly, the dead to speak, the self to dissolve, and sounds to become colors. The body accumulates materials; factual absence liberates the combinatorial degrees of freedom of those materials — together, they constitute the generative conditions for abstract thinking.

Chapter 3   The Covariance of Observational Tools and Philosophical Paradigms

Every major turning point in the history of human philosophy corresponds precisely to an upgrade in observational tools. Chapters 4 through 6 will demonstrate how humans acquired the cognitive capacity to transcend present facts and construct alternative world models — that is, the genesis of the capacity itself. This chapter, by contrast, demonstrates how, once that capacity had already formed, new observational tools forced existing world models to undergo content revision — that is, the historical evolution of theories. The former explains why humans can do philosophy; the latter explains why philosophy takes on different appearances in different eras. New tools alter cognitive inputs, and altered cognitive inputs force the reconstruction of philosophical frameworks.

3.1   The Naked-Eye Era → Elemental Philosophy and the Geocentric Universe

Humans initially possessed only the unaided eye. What could be seen was the regular motion of sun, moon, and stars; the transformations of water, fire, wind, and earth; and the cycles of birth, aging, illness, and death. Under these observational conditions, philosophy’s task was to infer invisible origins from visible appearances — Thales observed water’s ubiquity and concluded that “water is the principle of all things”; Heraclitus watched the dancing of flames and proposed that “everything flows.” Aristotle and Ptolemy built the geocentric system based on naked-eye observation of the heavens; the Platonic school insisted on modeling celestial cosmology with perfect circular motion — a model that dominated the human worldview for nearly 1,500 years. The limitations of the naked eye directly produced a static, hierarchically ordered, anthropocentric philosophical cosmology — the heavens were perfect and unchanging, the earth imperfect and mutable. This stratified order served as the foundation not only for astronomy but also for ethics and political philosophy.^[16]

3.2   The Telescope (1609) → The Copernican Revolution and Modern Philosophy

In 1609, Galileo pointed a telescope at the sky — the first qualitative leap in human observational instruments. He saw mountains and craters on the lunar surface — the moon was not smooth and perfect; Jupiter possessed its own system of satellites — the universe had more than one center; Venus displayed phases like those of the moon — a phenomenon the geocentric model could not explain. The telescope removed humanity from the center of the universe, challenging existing power structures and the ontological order. The invention of optical instruments revealed that the scope of human experience was not eternal and natural but contingent — it could change with the availability and performance of optical devices.^[16] This realization directly gave rise to the central question of modern philosophy: if what the naked eye sees has been deceiving us all along, what can we actually be certain of? Descartes’ “universal doubt” and “I think, therefore I am” were born precisely against this backdrop.

3.3   The Microscope → Mechanistic Philosophy

While the telescope was used to prove existing theories wrong, the microscope revealed that an entirely new set of theories had to be created. In the 17th century, Leeuwenhoek used the microscope to observe the microbial world, overturning the long-held belief that minute organisms spontaneously generated from some invisible substance — the microscope revealed that these organisms did in fact undergo normal reproductive processes. The philosophical consequence was that nature was no longer mysterious; everything could be explained by mechanical principles. This reinforced Descartes’ mechanistic worldview — the universe was a great machine, and all motion, from planetary orbits to blood circulation, obeyed the same mechanical laws. The telescope and the microscope also changed prevailing beliefs about “what humans can learn” — they were the first instruments to genuinely extend human senses, demonstrating that science and technology could reach places previously unimaginable.^[16]

3.4   Precision Instruments → Enlightenment Rationalism and Determinism

Newton used a prism to decompose white light into the seven-color spectrum and described universal gravitation with mathematical precision. The invention of precision clocks, barometers, and thermometers enabled humans to quantify natural phenomena. The philosophical consequence was a deterministic optimism: if all natural phenomena could be measured and calculated, then the universe was a predictable clockwork — given initial conditions, all future states could be computed. Laplace’s “demon” was the ultimate expression of this philosophy. Enlightenment philosophers extended this certainty to human society: since the laws of nature are rational, society too should be organized according to rational principles. The political philosophies of Locke, Rousseau, and Kant were all built upon this conviction.

3.5   Particle Detectors → The Collapse of Certainty and Quantum Philosophy

Particle accelerators, cloud chambers, and double-slit experimental apparatus allowed humans for the first time to “observe” the subatomic world — and the results rewrote philosophy entirely. According to the Copenhagen interpretation, a quantum particle exists in a state of superposition until measurement, and only at the moment of observation does the wave function collapse into a definite state. Heisenberg’s uncertainty principle tells us that position and momentum cannot both be precisely measured simultaneously — this is not a problem of insufficiently precise instruments but an intrinsic property of nature. The Newtonian deterministic worldview collapsed. The observer was no longer a bystander to the universe but a participant. The many-worlds interpretation holds that every possible quantum state manifests in a parallel reality, while the relational interpretation suggests that reality exists only in the interactions between observers.^[17]

3.6   Brain Imaging Technology → The Birth of Neurophilosophy

fMRI, PET, and other brain imaging technologies allowed humans for the first time to “see” the physical processes of thinking itself. One of the most important discoveries in neuroscience is that the brain possesses plasticity — it can change and adapt based on experience. This discovery gave rise to neurophilosophy as a new philosophical branch. When we can “see” which brain regions are active as a person makes a moral judgment, the philosophical concept of “free will” faces an unprecedented challenge. Every tool upgrade follows the same causal chain: new tool → new cognitive inputs → old philosophical framework becomes untenable → new philosophical system emerges.

3.7   The Problem of Theory-Ladenness

Chapter 4   Dreams: The First Channel of Abstract Thinking

4.1   The Human Record of Dreams: 2,000 Years Older Than Philosophy

Humanity’s systematic recording of dreams far predates any form of philosophical thinking. The earliest written dream records on Sumerian clay tablets date to approximately 3100 BCE.^[19] The dreams of Gudea, the priestly king who ruled Lagash around 2120 BCE, were inscribed on cuneiform tablets and constitute the earliest known detailed dream narratives.^[20] In the Assyrian Royal Library at Nineveh, archaeologists discovered nearly 2,500 tablets related to dreams.^[21] The Egyptian Chester Beatty Papyrus (c. 1220 BCE, from the Nineteenth Dynasty under Ramesses II) contains over 200 dream scenes and their interpretations.^[22] By 2000 BCE, Egypt had established a professional class of dream interpreters who served in temples and advised pharaohs.

The systematic recording of dreams preceded philosophy by at least 2,000 years. This temporal gap itself demonstrates a key thesis: humans were first struck by the “non-physical reality” experiences within dreams, and only later developed the capacity for systematic reflection on those experiences.

4.2   The Neural Mechanism of Memory Clearance: The Glymphatic System

A study published in Science in 2013 revealed the brain’s unique waste-removal mechanism — the glymphatic system — which becomes highly active during sleep.^[23] During deep sleep, brain cells temporarily shrink, creating more space between them and allowing cerebrospinal fluid to more effectively clear metabolic waste.^[24] More critically, the electrical waves that help sort, select, transport, and store memories simultaneously drive cerebrospinal fluid in and out of the brain — memory consolidation and physical cleansing are two sides of the same process.^[25]

4.3   Memory Reorganization and Abstraction During REM Sleep

A core function of sleep is the reorganization of neural information, enabling the brain to form new associations and discover patterns of meaning from past experience. Lewis et al. (2018) proposed a key framework: memory replay mechanisms during non-REM sleep abstract rules from the learned corpus of information, while replay during REM promotes novel associations. The iterative alternation of both throughout the night facilitates the formation and restructuring of complex knowledge frameworks.^[26] Associative thinking increases significantly during REM sleep.^[27] The bizarreness of dreams — the forced juxtaposition of unrelated things — is not a “malfunction” but precisely the subjective experience of the process of abstraction.

4.4   Dreams as a “Protoconsciousness” State

Hobson (2009), at Harvard, proposed that REM sleep activity constitutes a state of “protoconsciousness,” providing a functionally meaningful virtual-reality model of the world.^[28] A growing body of evidence suggests that REM sleep was critical to the evolution of uniquely human cognitive abilities: when Late Paleolithic ancestors gained greater access to REM sleep states, this helped initiate the process of cumulative cultural evolution.^[29]

4.5   The Causal Chain from Dreams to Metaphysical Intuition

Dreams provided humanity’s earliest experiences of “non-physical reality”: the dead returning to life in dreams → the origin of the concept of the soul; flight and metamorphosis in dreams → the origin of metaphysical questions about change and permanence; the distinction between dreaming and waking → the origin of ontological questions. Zhuangzi’s butterfly dream — “I do not know whether it was Zhuang Zhou dreaming he was a butterfly, or a butterfly dreaming it was Zhuang Zhou”^[30] — and Descartes’ dream argument^[31] represent the direct generation of metaphysical thought from dreams in the Eastern and Western philosophical traditions, respectively. Notably, several dreams that Descartes had as a young man are said to have embodied the program of theoretical doubt that he later developed in his Meditations — the seeds of modern philosophy may have been sown in dreams.^[32]

4.6   Post-Waking Comparison: The True Trigger of Abstract Thinking

Dreams do not automatically generate philosophical inquiry in and of themselves. Within a dream, the subject typically does not know they are dreaming — a stone turning into a bird, the dead speaking — these are accepted within the dream world as simply “the way things are.” The true epistemological shock occurs upon waking: the subject suddenly possesses two world models simultaneously — the dream world and the waking world — both of which once carried the full weight of reality, yet they contradict each other. A deceased companion was alive in the dream but dead in waking life. The self could fly in the dream but cannot in waking reality. This experience of “two once-real worlds that are mutually inconsistent” directly gave rise to humanity’s most primordial epistemological question: which one is real?

The philosophical power of Zhuangzi’s butterfly dream lies not in the image of becoming a butterfly during the dream, but in the inability upon waking to determine which side is the dream and which is waking reality. Descartes’ dream argument operates identically — “How do I know I am not dreaming right now?” is a question that only a subject who has experienced post-waking comparison can pose. Psychedelics push this comparison to an even more extreme form: you simultaneously know that you are standing on a grassland and see geometric patterns and morphing animals that do not exist — two worlds coexist at the same moment, and even the escape hatch of “waking up” is eliminated. Thus, the true trigger of abstract thinking is not the anomalous experience itself but the comparison between the anomalous experience and ordinary reality — it is precisely this comparison that forces the subject to construct a higher-order framework capable of accommodating both realities, and that framework is the prototype of metaphysics.

Chapter 5   Psychedelics: The Second Channel of Abstract Thinking

5.1   Cross-Species Evidence That Animals Universally Seek Altered States of Consciousness

The pursuit of altered states of consciousness is not a human “invention” but a cross-species biological drive. Felines — from domestic cats to tigers, leopards, and lynxes — are universally attracted to nepetalactone in catnip, displaying euphoria-like behavior.^[33] Dolphins have been observed gently handling pufferfish to obtain trace amounts of neurotoxin, then floating at the surface gazing at their own reflections.^[34] Jaguars consume ayahuasca plants containing DMT. African elephants and monkeys share fermented marula fruit. Caribbean vervet monkeys display drinking patterns strikingly similar to those of humans — a small number abstain entirely, the majority drink moderately, and a small proportion drink heavily — suggesting that the neural architecture driving addiction may be far older than the human species.^[35]

5.2   Archaeological Timeline of Human Psychedelic Use

Systematic human use of psychoactive substances preceded philosophy by at least five to six thousand years. Traces of San Pedro cactus found in the Guitarrero Cave in Peru date to 8600–5600 BCE.^[36] Prehistoric rock paintings in the Tassili n’Ajjer region of the Sahara Desert (c. 6000–4500 BCE) depict human figures grasping mushrooms, with dotted lines extending from the mushrooms toward their heads — possibly the earliest pictorial record of a psychedelic experience in human history.^[37] The earliest European evidence of opium poppy use comes from Italian Neolithic sites (c. 6000 BCE).^[36] In 2023, hallucinogenic alkaloids were directly detected in 3,000-year-old human hair found on the island of Menorca, Spain — the first direct evidence of prehistoric psychedelic use in Europe.^[38]

5.3   A Critical Evaluation of the “Stoned Ape” Hypothesis

McKenna (1992), in Food of the Gods, proposed that the ingestion of psilocybin mushrooms around 100,000 years ago catalyzed the cognitive leap from Homo erectus to Homo sapiens, sparking the birth of language, imagination, art, religion, and philosophy.^[39] While the hypothesis is intellectually stimulating, it has been criticized by the mainstream scientific community for lacking a falsifiable experimental design. However, the recent revival of psychedelic research has revealed significant cognitive effects of psilocybin at the chemical, physiological, neuroanatomical, and neuropsychological levels.^[40] This paper holds that the core intuition of McKenna’s hypothesis — that psychedelic experiences provided cognitive raw materials for abstract thinking — has merit, but needs to be reframed from a biological claim about “evolutionary catalysis” to a cognitive-scientific framework of “cognitive training grounds.”

5.4   The Unique Cognitive Functions Provided by Psychedelics

Psychedelics provide three unique functions that dreams cannot: First, hallucinations in a waking state — you know you are standing on a grassland but simultaneously see geometric patterns and morphing animals that do not exist. This “dual consciousness” is the prototypical operation of metaphysical thinking. Second, collective experience — a group of people simultaneously undergoes similar visions and can then discuss and compare them, providing the social foundation for shared abstract concepts. Third, repeatability — you cannot control what you dream about tonight, but you can decide to consume the same mushroom again, making systematic reflection on hallucinatory experience possible.

Chapter 6   Boredom and Social Pressure: The Dual Drivers of Abstract Thinking

6.1   The Abundant Leisure Time of Early Humans

Field research conducted by anthropologist Richard B. Lee among the San people of the Kalahari Desert demonstrated that hunter-gatherer societies spent only 12 to 19 hours per week on subsistence activities.^[41] Sahlins (1972) drew on this evidence to propose the concept of the “original affluent society.”^[42] Based on observations of extant hunter-gatherer societies, scholars estimate that early humans worked only 2.8 to 7.6 hours per day.^[43] After subtracting sleep, early humans still had 8 to 13 hours of waking leisure time each day — an enormous cognitive void that had to be “filled.” A study published in Nature Human Behaviour by Dyble et al. (2019) further confirmed that the transition from hunting and gathering to agriculture significantly reduced leisure time.^[44]

6.2   The Neural Mechanism of Boredom: Dopamine-Driven Novelty Seeking

From a neuroscientific perspective, boredom is not the absence of stimulation but an active psychological state. When dopamine levels drop due to a lack of stimulation, the brain begins seeking new challenges to restore equilibrium.^[45] A key finding is that the default mode network is highly active during boredom — the same neural network used for dreaming and creative thinking.^[46] An experiment by Mann and Cadman (2014) demonstrated that participants who completed a boring task subsequently performed better on tests of creative divergent thinking.^[47] Boredom forces the mind to spontaneously connect seemingly illogical and unrelated concepts — because the environment fails to provide sufficient stimulation, the mind must manufacture its own.

6.3   Social Relationships: Another Kind of “Factual Absence” Operation

Boredom is not the only driver of abstract thinking. Robin Dunbar’s social brain hypothesis reveals a parallel pathway: one of the core drivers of the expansion of the human neocortex was the need to process increasingly complex social relationship networks.^[75] In hunter-gatherer societies, individuals had to maintain a mental map of social relationships involving roughly 150 people — who is an ally, who cannot be trusted, who owes whom a favor, who is allied with whom. These relationships themselves constitute a form of “factual absence” operation: trust, loyalty, status, debt, and commitment are not physically visible objects; they cannot be pointed to with a finger, yet they must be modeled, tracked, and manipulated within the brain.

“Is he deceiving me?” “If I share food, will he reciprocate in the future?” “Does she treat him better than she treats me?” — These everyday social inferences are all counterfactual operations. One must simulate in one’s mind a scenario that has not yet occurred (“if I help him”), predict an internal state that cannot be directly observed (“is he loyal”), and make present-action decisions accordingly. Social intelligence, like dreams and psychedelics, trains the same core capacity — manipulating things that do not exist in the current physical environment. Boredom drives internal generation; social pressure drives the modeling of invisible relationships. From different directions, both push human cognitive operations away from the surface of present facts.

6.4   Boredom → Novelty Seeking → Psychedelic Experience → Dopamine Reward Loop

In the context of early humans, boredom-driven novelty seeking had three available reinforcement channels: social activities (mild stimulation), environmental exploration (moderate stimulation), and fermented beverages and psychoactive plants (intense stimulation, directly triggering surges in dopamine and serotonin). Psychoactive substances were repeatedly sought precisely because they provided the most extreme novel experiences without requiring physical displacement. Archaeological evidence indicates that the discovery and intensive use of psychoactive substances mostly occurred after the Neolithic Revolution — certain features of civilization itself (sedentism, leisure, social complexity) facilitated the systematization of psychedelic use.^[48]

6.5   The Unique Properties of Hallucinatory Memory

Psychedelic experiences constitute the most extreme violation of all existing expectations. Research in cognitive science has demonstrated that novel stimuli are more likely to differ from prior mental schemas, negating expectations and thus becoming more memorable.^[49] Hallucinatory memories are therefore exceptionally deep and enduring, and possess a unique property: they describe things that do not exist in the physical world. When early humans attempted to describe these experiences to their companions — “I saw something like a snake, but it was made of light” — they were forced to invent linguistic structures of the form “like… but not….” This structure is precisely the prototypical operation of metaphorical thinking and abstract language.

Chapter 7   A Taxonomy of Origins for Three Types of Thinking

7.1   Deductive Thinking: From the Necessities of the Physical World

Deductive thinking originates from repeated observation of necessary relations in the physical world. A released stone necessarily falls; fire necessarily produces heat. The core operation: “if A, then necessarily B.” If the premises are true, the conclusion must be true.^[50] Deductive thinking is reliable but lacks creativity — it merely applies existing rules to derive conclusions. Animals also possess basic causal reasoning abilities.

7.2   Inductive Thinking: From the Regularities of the Physical World

Inductive thinking originates from the accumulation of experiential observations of probabilistic relations in the physical world. Dark clouds usually bring rain; red berries are usually poisonous. The core operation: “observe multiple instances → extract patterns → predict the future.” Inductive reasoning does not guarantee absolute certainty but provides probable conclusions based on available evidence.^[50] Many animals possess sophisticated pattern-recognition and inductive abilities.

7.3   Purely Abstract / Metaphysical Thinking: From Experiences of “Factual Absence”

This paper proposes a third type of thinking whose source is neither the factual premises of deduction nor the empirical observations of induction, but rather the “factual absence” experiences provided by dreams, psychedelics, and meditation. Its core operation can be precisely formulated as follows: the identity rules and causal constraints of the current world no longer bind the representational relations within the alternative structure. In dreams, a stone transforms into a bird — this is not “the stone is simultaneously a stone and not a stone at the same time” — that would be a logical contradiction — but rather the stone’s identity has been reassigned under a different, temporarily operative set of world rules. The unique human capacity is not to violate logic but to construct an alternative set of temporarily operative world rules and maintain consistency within them. Imaginary numbers in mathematics are the ultimate manifestation of this capacity: mathematicians constructed an alternative rule system in which “a number whose square is negative” exists and then rigorously reasoned within that system — ultimately discovering that this alternative system happens to describe the deep structure of the physical world.

7.4   Counterfactual Thinking: The Cognitive-Scientific Counterpart of Metaphysical Thinking

“Counterfactual reasoning” in cognitive science — the capacity to “disengage from current reality, reason about events that would occur in alternative realities, and keep these alternative possibilities separate from actuality”^[51] — corresponds precisely to what this paper terms metaphysical thinking. Counterfactual reasoning is a hallmark capacity of human thought, enabling planning, creativity, and social attribution.^[52] This paper’s contribution lies in pointing out that the original training ground for this capacity was not in the waking physical world but in dreams, psychedelic experiences, and social-relationship reasoning.

7.5   Language: The Third Channel of Factual Absence

Language is not merely a tool for communicating dream and hallucinatory experiences — language itself is a “factual absence” engine that operates without closing one’s eyes. The conditional sentence (“if it rains tomorrow”) has no counterpart in the physical world — the very moment one utters this sentence, one is manipulating a nonexistent scenario. The subjunctive mood (“if I were king”) projects the subject into an identity that has never obtained. The negative sentence (“there is no apple on the table”) is the linguisticization of “nothing” — one uses language to point toward an object that does not exist. The structure of these everyday linguistic operations is fully isomorphic with the resurrection of the dead in dreams and the sensory cross-wiring in psychedelic states: all involve the reorganization of representations under conditions in which factual constraints have been lifted.

Dreams provide a passive channel of factual absence (automatically running every night); psychedelics provide an active channel (chemically induced); and language provides a controllable, high-speed, socialized third channel. More critically, language serves as the bridge between private anomalous experience and public abstract concepts: individual dreams and hallucinations are compressed through linguistic narration into shared concepts (“soul,” “afterlife,” “change,” “nothingness”), and shared concepts are then fixed through symbols into operable objects (“zero,” “infinity,” “imaginary numbers”). Without language as this intermediary, private experiences would forever remain at the individual level, unable to become civilization’s public tools. Language resolves the core transformational problem of “how does an individual’s hallucination become a collective consensus?”

7.6   The Key Difference Between Humans and Animals: The Reflective Loop

Animals also dream — MIT’s Wilson Lab demonstrated that during REM sleep, rats precisely replay their daytime maze experiences^[53] — and also seek psychoactive substances. But animals lack three key capacities:

The difference lies not in the experience itself but in the complete loop of “experience → memory → reflective processing → symbolization → pure symbolic operations detached from experience.” Animals are stuck at step two — they have experience but lack reflection on that experience.

Chapter 8   Zero: The Limiting Case of Purely Abstract Thinking

8.1   The Conceptual Difficulty of Zero

The invention of zero is one of humanity’s most profound mathematical achievements.^[7] Its conceptual difficulty resides in this: there is no direct physical mapping between “nothing” and the mathematical symbol “0.” You can point to three stones and say “three,” but you cannot point to anything and say “zero.” Transforming “nonexistence” itself into an operable number — a number that can participate in addition, subtraction, multiplication, and division — required an entirely new cognitive operation. Humanity learned to count long before it learned how to count “nothing.”^[57] Civilizations with sophisticated mathematics — Egypt, Greece, Rome — lacked zero because their number systems did not demand such a symbol.^[7]

8.2   The Multi-Stage Genesis Chain of Zero: Why the Greeks Could Not Do What the Indians Did

Zero was not a single act of invention but a multi-stage cultural-technological genesis process:

The critical question is: Why did Babylon have a placeholder yet never advance to the number zero? Why did the Maya have a concept of zero yet never develop a comparable algebraic system? Why did Greek mathematics, for all its brilliance, reject zero?^[58] The Greek obstacle was philosophical — Parmenides’ dictum “what is, is; what is not, is not” made it ontologically impossible to grant status to “nothing.” The Babylonian obstacle was functional — their sexagesimal system’s empty-position marker was a notational convenience, not an object of independent thought. The Mayan obstacle may have been one of transmission — in the absence of cross-civilizational knowledge flow, an isolated mathematical innovation was difficult to amplify into a complete algebraic system.

In India, however, long before zero was conceived of as a number, the philosophical concept of “void” (Śūnya) had already been taught and practiced through meditation in the Hindu and Buddhist traditions.^[59] The ancient Hindu symbol Bindu symbolized inner emptiness. “Nothingness” in meditation was not a lack but a state of consciousness actively sought and positively experienced. Indian mathematicians worked within a cultural tradition that was comfortable with the concept of “nothing” — and this cultural comfort lowered the conceptual resistance to objectifying “nonexistence” as an operable symbol.^[60] In 628 CE, Brahmagupta systematically specified the arithmetic rules for zero (including that any number plus zero equals itself, and any number multiplied by zero equals zero), completing the final leap from philosophical concept to mathematical object.

8.3   The Full Spectrum of Purely Abstract Concepts

8.4   The Paradox of “The More Abstract, the More Useful”

Imaginary numbers — Descartes coined the term “imaginary” in 1637 intending it as an insult — are today the mathematical foundation of AC circuit analysis, quantum mechanics, and signal processing.^[61] Zero — a concept that took humanity thousands of years to conceive — became the cornerstone of all modern computation in the form of binary encoding.^[62] Non-Euclidean geometry — regarded in the 19th century as a pure mathematical game — provides the relativistic corrections essential for precise positioning in GPS.^[63] Boolean algebra — developed by Boole in 1854 as a purely abstract exercise — became the logical foundation of digital and automation technology.^[64] The pattern is clear: the thinking least dependent on facts produced the most powerful tools for reshaping facts.

Chapter 9   The Concretization of “Idle Speculation” in Philosophy

In perfect parallel with mathematics, the most influential concepts in pure philosophy had no factual basis when they were first proposed — they were purely thought experiments or a priori constructs.

9.1   Political Philosophy

The “State of Nature” and Social Contract Theory

Hobbes, Locke, and Rousseau employed a thought tool called the “state of nature” — a picture of human life prior to political association.^[65] This scenario never existed (Hume and Burke explicitly characterized it as “complete fiction”^[66]), yet it gave rise to the American Declaration of Independence, the French Declaration of the Rights of Man and of the Citizen, and all modern constitutional democracies. The journey from Grotius to the Universal Declaration of Human Rights demonstrates that abstract theories of inherent dignity and natural rights acquired urgent practical significance in the aftermath of World War II.^[67]

Rawls’ “Veil of Ignorance”

Rawls (1971) asks us to imagine designing social institutions without knowing what position we will occupy in that society — a logically impossible scenario.^[68] Research spanning seven experiments with over 6,000 participants has validated the practical efficacy of this purely theoretical thought experiment: veil-of-ignorance reasoning inclines people toward choices that favor the greater public good, including more effective charitable giving and the ethical programming of autonomous vehicles.^[69]

9.2   Ethics

Kant’s Categorical Imperative

Kant’s moral law is purely a priori — derived non-empirically from the very structure of practical reason itself.^[70] The core formula — “act only according to that maxim whereby you can at the same time will that it should become a universal law” — derives from no empirical observation.^[71] This purely abstract moral principle directly influenced the Universal Declaration of Human Rights (1948), the International Covenant on Civil and Political Rights (1966), and the International Criminal Court (2002).^[72]

Utilitarianism

“The greatest happiness of the greatest number” — the “happiness” in this formula cannot be precisely quantified. Yet this unquantifiable, purely abstract principle has been concretized as: cost-benefit analysis in modern public policy, the QALY system in healthcare resource allocation, and ethical algorithms for autonomous vehicles.^[73]

9.3   Methodology

Dialectics

Hegel’s dialectical movement — determination (Bestimmung) → negation (Negation) → sublation (Aufhebung) — is a purely abstract model of the movement of thought (commonly simplified in popular usage as “thesis → antithesis → synthesis,” though Hegel himself did not use this formula). No object in the physical world “negates itself” and then “achieves unity at a higher level.” This speculative movement is entirely thought’s abstract description of its own process, with no basis in empirical fact. Yet once concretized, Marx transformed it into historical materialism and the theory of class struggle, directly shaping the political systems of multiple nations in the 20th century. The cycle of “hypothesis → refutation → new hypothesis” in scientific methodology is also a practical variant of dialectics, serving as the core engine driving the progress of knowledge.

Occam’s Razor

“Entities should not be multiplied beyond necessity” — this is not an empirical discovery but a pure methodological preference. No law of physics requires the universe to be simple; the preference for simpler explanations is essentially an aesthetic intuition. Yet this aesthetic intuition, once concretized, became the core methodological principle of all modern science, guiding theoretical choices in everything from particle physics to biology. In the field of machine learning, the principle of regularization (penalizing overly complex models) and the medical diagnostic maxim “when you hear hoofbeats, think horses, not zebras” are both direct applications of Occam’s Razor.

Descartes’ Universal Doubt

Doubt everything that can be doubted until one finds something that cannot be doubted — Descartes conceived this method while sitting beside a stove; it had no empirical basis and was a purely intellectual operation. Yet once concretized, it became the philosophical foundation of modern scientific peer review (every claim must withstand systematic challenge) and the legal standard of “beyond a reasonable doubt” — a verdict can stand only after all reasonable doubts have been eliminated. An idle thought conceived by a stove ultimately became the institutional cornerstone safeguarding scientific integrity and judicial justice.

9.4   Ontology

Plato’s Theory of Forms — no perfect circle or perfect justice exists in the physical world. “Perfect Forms” exist in a world of Ideas inaccessible to the senses. No one has ever seen this world. Yet it has been concretized as: the ISO standardization system, the “reasonable person” standard in law, and axiomatic mathematics — all practical applications of the principle that “imperfect reality is measured against an ideal standard.”^[74]

Chapter 10   Conclusion: From Dreams to Civilization

10.1   The Complete Formulation of the Unified Theory

10.2   The Core Paradox

The deepest paradox this paper reveals is that the deep structure of the physical world is “counterfactual.” The way reality truly operates — quantum superposition, curved spacetime, wave-particle duality — cannot be understood through common sense and factual observation. It can only be grasped through the kind of purely abstract thinking that was originally trained in dreams and hallucinations. Imaginary numbers were considered “impossible” in the 16th century — 400 years later, they appeared at the heart of the foundational equations of quantum mechanics. Humans learned in their dreams to imagine the impossible — and then discovered that the universe itself is constituted by the impossible.

10.3   A Correction to the Narrative of the History of Philosophy

The traditional history of philosophy begins with Thales, treating the transition “from myth to reason” as the starting point of philosophy. This paper argues that this narrative omits tens of thousands of years of cognitive prehistory. For tens of thousands of years before Thales, the human brain reorganized information in dreams every night and periodically experienced “another reality” through psychoactive substances — these experiences were the true cognitive soil of philosophical thinking. Philosophy was not the invention of some individual genius but the ultimate product of exceedingly basic biological processes: the brain clearing memory, coping with boredom, and processing hallucinations.

10.4   Implications for Contemporary AI and Consciousness Research

If the origin of abstract thinking lies in experiences of “factual absence” and recursive reflection on those experiences, can artificial intelligence that is trained purely on data ever truly develop abstract thinking? Current large language models are trained on massive corpora of text and possess powerful pattern-recognition, deductive, and inductive capabilities, but they have never “dreamed,” never “experienced nothingness,” and never seen “things that do not exist” in a hallucinatory state. Does this mean that AI under the current paradigm is, in principle, unable to reach purely abstract thinking? This question bears significant implications for understanding the nature and limits of AI.

10.5   One-Sentence Summary