Appendix A: The Taxonomy of Knowledge – How Subjects Relate for the Sarvartharthapedia Subject Guide for Human Understanding.
APPENDIX A: THE TAXONOMY OF KNOWLEDGE
How Subjects Relate – A Map of Human Understanding
Before the Map: A Warning
No taxonomy of knowledge is final. Disciplines bleed into each other. New fields are born at the borders. What follows is not a prison but a scaffold — a way to see the shape of the whole before you climb into any single branch.
Think of this as a tree, but a tree where roots touch branches and every leaf connects to every other by underground mycelium.
LEVEL 0: THE THREE GREAT DIVISIONS
All human knowledge can be roughly divided into three domains, though the boundaries are contested.
The Formal Sciences deal with abstract systems of symbols, logic, and structure. They do not depend on the physical world for their truth. Mathematics, logic, computer science, and parts of statistics live here. Their truths are necessary — they could not be otherwise.
The Natural Sciences deal with the physical world: matter, energy, life, and the cosmos. Physics, chemistry, biology, earth sciences, and astronomy live here. Their truths are contingent — they could have been otherwise, and we discover them through observation and experiment.
The Human Sciences (sometimes called the social sciences and humanities) deal with human meaning, culture, society, and experience. Anthropology, sociology, history, economics, political science, psychology, philosophy, and the arts live here. Their truths are interpretive — they depend on context, perspective, and the meanings humans create.
No single subject lives entirely in one division. Psychology straddles natural science (neuroscience, behavior) and human science (consciousness, meaning). Economics straddles formal science (game theory, mathematical models) and human science (institutions, behavior, justice). Computer science straddles formal science (algorithms, computability) and natural science (hardware, robotics) and increasingly human science (AI ethics, human-computer interaction).
The divisions are useful fictions. Use them to orient yourself, then ignore them.
LEVEL 1: THE ROOTS – FORMAL SCIENCES
These are the foundations. They provide the grammar and tools for all other knowledge. Without them, reasoning collapses into contradiction and measurement into chaos.
Mathematics is the study of pattern, structure, and quantity. It is the oldest formal science. Its branches include arithmetic (numbers), algebra (relations), geometry (space), analysis (change), topology (continuity), and logic (valid inference). Mathematics does not describe the physical world directly — but physics cannot function without it.
Logic is the study of valid reasoning. It provides the rules that distinguish good arguments from bad ones. Deductive logic gives certainty (if premises are true, conclusion must be true). Inductive logic gives probability (the sun has risen every day, so it will rise tomorrow). Abductive logic gives explanation (the best guess given the evidence). Logic is to philosophy what mathematics is to physics.
Statistics is the mathematics of uncertainty. It provides the tools for making inferences from samples to populations, for measuring the strength of evidence, and for quantifying risk. Every science that deals with variation (which is every science) depends on statistics.
Computer Science is the study of computation: what can be computed, how efficiently, and by what means. Its core includes algorithms (step-by-step procedures), data structures (ways to organize information), programming languages (formal systems for instructing machines), and complexity theory (the inherent difficulty of problems). Computer science has transformed every other field — from biology (bioinformatics) to history (digital humanities) to art (generative AI).
Decision Theory and Game Theory are the formal sciences of choice. Decision theory studies how a single rational agent should choose among options under uncertainty. Game theory studies how multiple rational agents choose when their outcomes depend on each other’s choices. These fields bridge formal logic, economics, psychology, and political science.
LEVEL 2: THE TRUNK – NATURAL SCIENCES
The trunk of the tree divides into matter (physics and chemistry) and life (biology), but the two are continuous.
Physics: The Most Fundamental
Physics asks: What is the universe made of, and what are the laws that govern it?
At the largest scale, cosmology studies the origin, structure, and fate of the universe: the Big Bang, dark matter, dark energy, galaxies, and cosmic background radiation.
At the scale of stars and planets, astrophysics and planetary science study celestial bodies: their composition, motion, atmospheres, and potential for life.
At the human scale, classical mechanics (motion, forces, energy), thermodynamics (heat, work, entropy), and electromagnetism (electricity, magnetism, light) describe most of everyday experience.
At the smallest scale, quantum mechanics describes the bizarre behavior of atoms, electrons, photons, and the fundamental particles. Particle physics (high-energy physics) studies the elementary constituents of matter — quarks, leptons, bosons — and the forces between them.
Condensed matter physics studies the properties of solids and liquids: superconductivity, magnetism, crystals, and the materials that make modern technology possible.
Physics provides the laws that chemistry and biology must obey. But physics cannot, by itself, explain a cell or a consciousness. Higher-level sciences are autonomous — they have their own concepts and laws that are not reducible to physics, even though they are consistent with it.
Chemistry: The Bridge
Chemistry asks: How do atoms combine into molecules, and how do molecules transform?
Inorganic chemistry studies compounds that do not contain carbon: metals, salts, minerals, and industrial catalysts.
Organic chemistry studies carbon-based compounds — the molecules of life (proteins, carbohydrates, fats, DNA) and also plastics, pharmaceuticals, and fuels.
Physical chemistry applies physics to chemical systems: reaction rates (kinetics), energy changes (thermodynamics), and quantum behavior of molecules.
Analytical chemistry develops tools to identify and measure substances: chromatography, spectroscopy, mass spectrometry.
Biochemistry is the chemistry of living systems: enzymes, metabolism, signal transduction, and the molecular machines inside cells. It is the bridge between chemistry and biology.
Biology: The Study of Life
Biology asks: What is life, and how does it work, change, and interact?
At the smallest scale, molecular biology studies the molecules of life: DNA, RNA, proteins, and their interactions. It explains how genetic information is stored, copied, and expressed.
Cell biology studies the basic unit of life: the cell. How do cells move, divide, communicate, and die? How do organelles (nucleus, mitochondria, chloroplasts) work together?
Genetics studies heredity: how traits are passed from parents to offspring, how genes mutate, and how variation arises. Genomics extends this to the entire genome — all the genetic material of an organism.
Developmental biology asks: How does a single fertilized egg become a complex, multi-celled organism with specialized tissues and organs?
Physiology studies how organisms function: how hearts pump, lungs breathe, neurons fire, and kidneys filter. It is the biology of systems.
Anatomy studies the structure of organisms: bones, muscles, organs, and their spatial relationships. Anatomy without physiology is a map without movement; physiology without anatomy is function without form.
Evolutionary biology is the great unifying theory of all life. It asks: How do species change over time? How does natural selection shape adaptations? Why do we see the patterns we see in the tree of life?
Ecology studies the interactions between organisms and their environments: populations, communities, ecosystems, and the biosphere. It asks: How do energy and nutrients flow? How do predators and prey coexist? What happens when a species is removed or added?
Ethology (animal behavior) studies what animals do: why birds sing, why bees dance, why wolves hunt in packs. It overlaps with psychology (when the animal is human) and with neuroscience (when the behavior is traced to the brain).
Taxonomy and systematics are the sciences of classification: naming organisms (nomenclature), grouping them by evolutionary relationship (phylogeny), and building the tree of life.
Paleontology studies ancient life through fossils. It is the bridge between biology and geology: evolution written in stone.
Microbiology studies organisms too small to see with the naked eye: bacteria, archaea, viruses, protists, and fungi. It is the foundation of infectious disease medicine and much of biotechnology.
Botany (plant biology) and zoology (animal biology) are traditional divisions based on kingdom. They are being absorbed into more functional divisions (molecular, ecological, evolutionary) but remain useful for teaching and field research.
Earth and Environmental Sciences
Geology studies the solid Earth: rocks, minerals, plate tectonics, volcanoes, earthquakes, and the planet’s 4.5-billion-year history.
Oceanography studies the oceans: currents, chemistry, marine life, seafloor geology, and the ocean’s role in climate.
Atmospheric science studies the air: weather, climate, storms, and the chemistry of the atmosphere.
Environmental science is the interdisciplinary study of the natural world and human impacts upon it: pollution, conservation, climate change, and sustainability. It draws on biology, chemistry, geology, and the social sciences.
LEVEL 3: THE BRANCHES – HUMAN SCIENCES
These are the sciences of human meaning, behavior, and society. They are messier than the natural sciences — their laws have exceptions, their predictions are probabilistic, and their objects of study talk back.
Psychology: The Science of Mind and Behavior
Psychology asks: What is the mind? How do we perceive, think, feel, and act?
Cognitive psychology studies mental processes: attention, memory, reasoning, decision-making, problem-solving, and language. It asks: How do we represent the world in our minds?
Developmental psychology studies how humans change across the lifespan: from infant attachment to adolescent identity to aging and wisdom.
Social psychology studies how we are influenced by others: conformity, obedience, persuasion, group dynamics, prejudice, and attraction.
Clinical psychology studies mental health and illness: depression, anxiety, schizophrenia, trauma, and their treatment through therapy.
Personality psychology studies individual differences: traits (the Big Five: openness, conscientiousness, extraversion, agreeableness, neuroticism), motivations, and the stable patterns that make each person unique.
Neuroscience (biological psychology) studies the brain and nervous system. It is the bridge between psychology and biology. Cognitive neuroscience links mental processes to brain activity.
Abnormal psychology studies patterns of behavior, emotion, and thought that deviate from cultural norms and cause distress or impairment.
Sociology: The Science of Social Life
Sociology asks: How do groups, institutions, and social structures shape human behavior?
Social structure is the enduring pattern of relationships and institutions that organizes society: class, race, gender, family, education, economy, polity.
Social inequality studies the unequal distribution of resources, power, and prestige: poverty, wealth concentration, social mobility, and the reproduction of privilege across generations.
Institutions are the stable, organized systems of social life: the family, education, religion, the economy, the state, and the media. Each has its own norms, roles, and power dynamics.
Social change studies how societies transform: revolutions, social movements, demographic shifts, technological change, and cultural evolution.
Urban sociology studies cities: how they grow, how they segregate, how they create both opportunity and alienation.
Political sociology studies the relationship between society and the state: power, social movements, voting behavior, and the social bases of political parties.
Economic sociology studies the social foundations of economic activity: how trust, networks, and culture shape markets, firms, and consumption.
Cultural sociology studies meaning: how symbols, values, beliefs, and practices are produced, maintained, and contested.
Anthropology: The Science of Humanity in Full
Anthropology asks: What does it mean to be human, across all time and all places?
Cultural anthropology studies living human cultures through ethnography — living with people, learning their language, participating in their lives. It asks: How do people in different societies make meaning, organize kinship, practice religion, and produce art?
Archaeology studies past human societies through their material remains: tools, pottery, buildings, bones, and landscapes. It is the anthropology of the dead.
Biological anthropology studies human evolution, primatology, human genetics, and human biological variation. It asks: How did we become human? How are we related to other primates? Why do human bodies vary across populations?
Linguistic anthropology studies language as a cultural resource: how language shapes thought, how people use language to perform identity, and how languages change and die.
Applied anthropology uses anthropological methods to solve practical problems: public health, development, education, business, and cultural heritage preservation.
Anthropology is unique in its holism — it tries to understand humans as biological, social, cultural, historical, and linguistic beings all at once.
Economics: The Science of Scarcity and Choice
Economics asks: How do societies allocate scarce resources among competing wants?
Microeconomics studies individual economic agents: households, firms, and markets. It asks: How do prices emerge from supply and demand? How do firms decide what to produce? How do consumers decide what to buy?
Macroeconomics studies the economy as a whole: inflation, unemployment, economic growth, trade, and the business cycle. It asks: Why do recessions happen? How can governments use fiscal and monetary policy to stabilize the economy?
Behavioral economics integrates psychology into economics: it studies how cognitive biases, emotions, and social norms cause real human behavior to deviate from the rational actor model.
Development economics studies poverty, growth, and policy in low-income countries. It asks: Why are some countries rich and others poor? What interventions actually help?
International economics studies trade, finance, and migration across borders. It asks: Who gains and who loses from globalization?
Public economics studies government policy: taxation, social insurance, public goods, and externalities.
Labor economics studies work, wages, employment, and discrimination.
Environmental economics studies the economics of natural resources, pollution, and climate change.
Political Science: The Science of Power and Governance
Political science asks: Who gets what, when, and how? How do we govern ourselves, and how should we?
Political theory asks normative questions: What is justice? What is liberty? What is democracy? It draws on philosophy, history, and law.
Comparative politics compares political systems across countries: democracies vs. autocracies, presidential vs. parliamentary systems, and the causes of democratization, revolution, and civil war.
International relations studies politics among nations: war, peace, diplomacy, trade, international law, and global institutions like the United Nations. Its major theories include realism (power matters most), liberalism (institutions and interdependence matter), and constructivism (ideas and identities matter).
Public administration studies the implementation of policy: bureaucracy, government agencies, and the challenges of making policy work in practice.
Public policy studies the content and consequences of government action: health policy, education policy, environmental policy, and social welfare policy.
Political methodology develops the statistical and formal tools used to study politics: causal inference, game theory, and survey research.
Geography: The Science of Space and Place
Geography asks: Where things are, why they are there, and why it matters.
Physical geography studies the natural environment: landforms, climate, vegetation, soils, and hydrology. It overlaps with earth sciences.
Human geography studies the spatial organization of human activity: cities, agriculture, industry, transportation, and cultural regions. It asks: Why do cities grow where they do? How do people organize space? What is the relationship between place and identity?
Geographic Information Science (GIS) develops the tools for capturing, analyzing, and visualizing spatial data. It is the technical backbone of modern geography.
Environmental geography studies human-environment interaction: resource use, pollution, conservation, and the human dimensions of climate change.
Geopolitics studies the relationship between geography and political power: borders, resources, strategic chokepoints, and territorial conflict.
History: The Science of Change Over Time
History asks: What happened in the past, and why does it matter for the present?
Political history studies states, wars, leaders, and institutions. It is the oldest form of history.
Social history studies ordinary people, social structures, and everyday life: family, work, migration, and community.
Economic history studies economies in the past: trade, industry, agriculture, and the material conditions of life.
Cultural history studies meaning, values, and representation: art, literature, religion, and popular culture over time.
Intellectual history studies ideas: how concepts like freedom, equality, and justice have been understood and debated across centuries.
Gender history studies the role of gender in the past: how masculinity and femininity have been constructed, how women have been excluded and included.
Global history studies connections across regions and civilizations: trade routes, empires, migrations, and the circulation of ideas and diseases.
Public history applies historical methods outside the academy: museums, archives, historic preservation, oral history, and digital humanities.
Historiography is the history of history: how historians have written about the past, how methods have changed, and how biases have shaped what we remember.
LEVEL 4: THE LEAVES – APPLIED & INTERDISCIPLINARY FIELDS
These fields draw on multiple branches of the tree. They are not “pure” disciplines but responses to real-world problems.
Health and Medicine
Medicine is the applied science of healing. It draws on biology (anatomy, physiology, genetics), chemistry (pharmacology), psychology (mental health, patient behavior), and sociology (health disparities, health systems).
Public health studies the health of populations, not just individuals. It draws on epidemiology (disease patterns), biostatistics, environmental health, health policy, and behavioral science.
Nursing is both a science (evidence-based practice) and an art (compassionate care). It focuses on the whole person, not just the disease.
Pharmacy is the science of preparing and dispensing drugs. It draws on chemistry, biology, and pharmacology.
Dentistry, veterinary medicine, optometry, physical therapy — each is an applied field with its own body of knowledge and clinical skills.
Engineering and Technology
Engineering is the application of scientific principles to design and build things that solve practical problems.
Civil engineering builds infrastructure: bridges, roads, dams, buildings, water systems.
Mechanical engineering designs machines: engines, robots, HVAC systems, manufacturing equipment.
Electrical engineering designs electrical and electronic systems: power grids, motors, circuits, computers.
Chemical engineering transforms raw materials into useful products: fuels, plastics, pharmaceuticals, food.
Computer engineering designs computer hardware and embedded systems.
Software engineering designs computer programs and systems.
Biomedical engineering applies engineering to medicine: prosthetics, medical imaging, artificial organs, drug delivery systems.
Environmental engineering designs solutions for pollution control, water treatment, waste management, and sustainable infrastructure.
Law and Justice
Law is the system of rules that societies create to govern behavior, resolve disputes, and protect rights.
Criminal law defines crimes and punishments. It draws on philosophy (theories of punishment), sociology (crime and deviance), psychology (criminal behavior), and political science (the state’s power to punish).
Civil law governs disputes between private parties: contracts, property, torts (injuries), family law (marriage, divorce, custody).
Constitutional law interprets the fundamental charter of government. It draws on history, political theory, and philosophy.
International law governs relations between states: treaties, human rights, war crimes, the law of the sea.
Legal theory asks: What is law? When are we obliged to obey? How should judges interpret statutes and constitutions?
Education
Education is the science and art of teaching and learning.
Curriculum theory asks: What knowledge is most worth? Who decides? How should knowledge be organized for learning?
Pedagogy is the study of teaching methods: direct instruction, inquiry-based learning, project-based learning, Montessori, Waldorf, and many others.
Educational psychology studies how children learn, how to motivate students, how to assess learning, and how to address learning difficulties.
Educational policy studies school funding, standards, testing, teacher preparation, and school choice.
Comparative education studies educational systems across countries: what works, what does not, and why.
Business and Management
Business is the organization of human activity for the production and exchange of goods and services.
Management studies how to organize people and resources to achieve goals: leadership, strategy, operations, human resources, and organizational behavior.
Marketing studies how to understand and satisfy customer needs: market research, branding, advertising, pricing, and distribution.
Finance studies the management of money: investments, risk, banking, corporate finance, and financial markets.
Accounting measures and communicates financial information: bookkeeping, auditing, financial reporting.
Entrepreneurship studies how new ventures are created, funded, and scaled.
Communication and Media
Communication studies the production, transmission, and reception of messages.
Journalism gathers, verifies, and reports information for public audiences. It is the practice of informing citizens in a democracy.
Media studies analyzes media content, industries, and audiences: television, film, digital media, social media, and their effects on culture and politics.
Rhetoric is the art of persuasion: how to craft arguments, use language effectively, and adapt to audiences.
Public relations manages the flow of information between organizations and the public.
Advertising creates persuasive messages to promote products, services, or ideas.
Interpersonal communication studies face-to-face interaction: conversation, relationship development, conflict, and nonverbal behavior.
LEVEL 5: THE MYCELIUM – CONNECTIONS BETWEEN FIELDS
No field stands alone. Here are some of the most productive connections.
Cognitive science connects psychology, neuroscience, computer science (AI), linguistics, and philosophy. It asks: How does the mind work? It is the mycelium that runs beneath many separate disciplines.
Environmental studies connects ecology (biology), earth science, economics (externalities, valuation), political science (policy, governance), sociology (environmental justice), and ethics (our obligations to future generations and other species).
Gender studies connects sociology (gender as social structure), history (histories of women and LGBTQ+ people), literature (representation), psychology (gender identity), law (discrimination, rights), and philosophy (feminist theory).
Postcolonial studies connects history (colonialism), literature (colonial and postcolonial writing), political science (nation-building, imperialism), anthropology (culture contact, hybridity), and philosophy (decolonizing knowledge).
Science and technology studies (STS) connects sociology (laboratories as social systems), history (how science changed over time), philosophy (epistemology, realism vs. constructivism), and anthropology (how scientific knowledge is made).
Urban studies connects geography (spatial patterns), sociology (segregation, community), economics (housing markets, labor markets), political science (urban governance, planning), engineering (infrastructure, transportation), and environmental science (urban ecology, heat islands).
Food studies connects agriculture (plant science, animal science), nutrition (medicine, biochemistry), economics (food systems, trade), sociology (food justice, food culture), history (cuisine, famine), and anthropology (food rituals, taboos).
Data science is not a field but a method applied everywhere. It connects computer science (algorithms, databases), statistics (inference, prediction), mathematics (linear algebra, optimization), and domain knowledge (any field to which it is applied).
LEVEL 6: THE METADISCIPLINES – THEORIES OF KNOWLEDGE ITSELF
These fields do not study a piece of reality. They study how we study.
Epistemology asks: What is knowledge? What justifies belief? What is the difference between science and pseudoscience?
Philosophy of science asks: What is a scientific explanation? How do theories relate to evidence? Do unobservable entities (electrons, quarks) really exist?
Historiography asks: How do historians know what they claim to know? How do historical narratives shape our understanding of the past?
Sociology of knowledge asks: How do social factors (class, race, gender, institutions) shape what a society takes for granted as true?
Anthropology of knowledge asks: How do different cultures define knowledge, wisdom, and expertise?
Library and information science asks: How should knowledge be organized, classified, stored, and retrieved so that it is useful?
Cognitive science of science asks: How do scientists think? What cognitive biases help and hinder discovery?
Research methodology is not a subject but a toolkit of methods that cut across all subjects: observation, measurement, experiment, survey, interview, archival research, modeling, simulation, and statistical inference.
LEVEL 7: THE SOIL – THE HUMANITIES
The humanities are not sciences. They do not produce testable predictions or general laws. They produce understanding, interpretation, wisdom, and beauty.
Philosophy is the most foundational of the humanities. It asks questions that science cannot answer: What is the good life? What is justice? What is consciousness? Does God exist? It proceeds by argument, not experiment.
Literature is the art of written language. It asks: What is it like to be another person in another time and place? Literature provides vicarious experience — the closest we can get to living many lives. It includes poetry (compressed, musical language), fiction (imagined narratives), drama (dialogue and action for the stage), and creative nonfiction (true stories told with literary craft).
History (already covered) is both a social science (causal explanation) and a humanity (interpretation, narrative, meaning).
Art history studies visual art across time and culture: painting, sculpture, architecture, photography, and new media. It asks: What did this artwork mean to its original audience? How does it use form, color, and composition? How does it reflect its social context?
Musicology studies music as a human practice: its history, its theory (harmony, rhythm, form), its performance, and its meaning.
Theology and religious studies study religion from within (theology: faith seeking understanding) and from without (religious studies: the academic, comparative, often secular study of religious beliefs, practices, and institutions).
Classics studies the ancient Greek and Roman worlds: their languages (Greek, Latin), literature, philosophy, history, art, and archaeology.
Linguistics (the scientific study of language) straddles the humanities (interpretation of texts) and the cognitive sciences (language as a mental faculty).
AFTERWORD: HOW TO USE THIS MAP
You are here. You have climbed the tree from roots to soil.
Do not memorize this taxonomy. Use it as a tool for orientation.
When you encounter a new subject, ask:
- What does it study? (Its object)
- How does it study? (Its method)
- What does it assume? (Its foundations)
- What does it connect to? (Its neighbors)
And remember: The map is not the territory. The tree is not the forest. The taxonomy is a tool for understanding — but the real world, the real human experience, is messier, richer, and more connected than any classification can capture.
The best use of this map is to get lost — to wander from mathematics to poetry to neuroscience to history — and to discover connections that no taxonomy could have predicted.
That is not a failure of the taxonomy. That is the point.
End of Appendix A: The Taxonomy of Knowledge – How Subjects Relate
