Before You Think: The Foundations That Make Thinking Possible

You want to understand how we know anything at all, what reality is made of, and why logic is the grammar that holds both questions together. This path gives you the structural foundation of philosophy — not a history of opinions, but the load-bearing framework underneath every serious claim about the world.

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Who this is for

You are not looking for a timeline of famous philosophers. You are looking for the architecture of thought itself — the questions every school of philosophy must answer, and how their answers to one question force their answers to the others. You suspect that epistemology, logic, and metaphysics are not three separate subjects but three faces of the same problem. You are right.

What this article is NOT

This is not a history of philosophy and not a survey of “who said what.” It is the structural substrate — the questions, the bets, the dependencies between them. Philosophers appear because they crystallised ideas, not because you need to memorise their names.

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Part 1 — The problem of knowing

Part 1

Before you can claim to know anything about the world, you need an answer to a harder question: what counts as knowing in the first place?

You believe that Paris is the capital of France. This belief happens to be true. And you have good reasons for holding it — you have seen maps, read books, perhaps visited the city. Does that mean you know it?

For roughly two thousand years, philosophers said yes. The standard answer, traceable to Plato’s Theaetetus, was the tripartite definition: knowledge is justified-true-belief. Three conditions, all required.¹

graph LR
    B[Belief<br/>you hold it] --> J[Justification<br/>you have reasons]
    J --> T[Truth<br/>it matches reality]
    T --> K[Knowledge]

    style K fill:#5cb85c,color:#fff

Condition	What it demands	What fails without it
Belief	You must actually hold the proposition	You cannot know something you do not believe
Truth	The proposition must be true	A well-reasoned falsehood is not knowledge
Justification	You must have good reasons	A lucky guess, even if true, is not knowledge

This looks clean. It is not.

The Gettier rupture

In 1963, Edmund Gettier published a three-page paper that broke the tripartite definition.² He constructed cases where someone has a justified true belief and still, by any reasonable intuition, does not know.

Here is the structure of a Gettier case: you believe P for justified reasons. P happens to be true. But the connection between your justification and the truth is accidental — your reasons are right by luck, not by tracking reality.

Imagine you look across a field and see what appears to be a sheep. You form the justified belief “there is a sheep in the field.” There is indeed a sheep in the field — but behind a hill, invisible to you. What you saw was a dog wearing a sheepskin coat. Your belief is justified. Your belief is true. But you do not know there is a sheep in the field, because your justification has nothing to do with why the belief is true.³

Why this matters

The Gettier problem is not a puzzle for academics. It reveals something structural: justification and truth can come apart. You can do everything right and still not know. This forces a question that echoes through every part of philosophy: what bridges the gap between our reasons and reality?

Epistemologists have spent sixty years proposing solutions — adding a fourth condition, strengthening justification, abandoning the whole framework.⁴ None has achieved consensus. The gap remains open.

The rest of this path is about how different traditions approach that gap.

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Part 2 — The rationalist bet

Part 2

Some truths seem to arrive without experience. Mathematics, logic, the structure of space. Rationalism bets that reason alone can reach genuine knowledge about reality — and this bet has consequences for everything else.

Rene Descartes asked the most radical question in epistemology: what survives if you doubt everything?⁵

His method was systematic demolition. Senses deceive — eliminate them. Memory fails — eliminate it. You might be dreaming right now — eliminate all experience. An evil demon might be feeding you a false reality — eliminate even the apparent structure of the world.

What survives? Only this: the act of doubting itself proves that something is doing the doubting. Cogito ergo sum — I think, therefore I am. Not “I exist as a body” or “I exist in this room,” but “something that thinks exists.” That is the foundation.⁵

graph TD
    D[Doubt everything] --> S[Senses can deceive]
    D --> M[Memory can fail]
    D --> DR[You might be dreaming]
    D --> DM[An evil demon might<br/>fabricate reality]
    S --> C[What survives?]
    M --> C
    DR --> C
    DM --> C
    C --> CO[Cogito<br/>the thinking itself]

    style CO fill:#4a9ede,color:#fff

From this foundation, rationalism builds outward. If the most certain knowledge you have arrived without any sensory experience, then reason — not observation — is the primary source of knowledge. Descartes argued that certain ideas are innate: the idea of God, the principles of mathematics, the concept of infinity. These are not learned from experience. They are part of the architecture of a thinking mind.⁶

Leibniz pushed this further. Experience might occasion the recognition of an innate idea, the way striking a bell makes it ring, but the capacity for that particular sound was always in the bell. The mind comes pre-structured.⁶

The metaphysical cost

This bet has a price. If reason can reach truths about reality independently of experience, then reality must have a rational structure that reason can access. The rationalist is committed to a metaphysics where the universe is fundamentally intelligible — where the deep structure of things corresponds to the deep structure of thought.

Descartes paid this price explicitly: he divided reality into two substances, mind (res cogitans) and matter (res extensa), each with its own nature, each knowable on its own terms. The physical world is mathematical in structure. The mind has direct access to mathematical and logical truths. This is not a coincidence — it is the architecture of reality.⁵

Go deeper

The rationalist commitment has a direct descendant in modern science: the “unreasonable effectiveness of mathematics” that Eugene Wigner noted in 1960. The fact that equations written on paper predict the behaviour of distant galaxies is either a cosmic coincidence or evidence that rationalism was onto something structural.

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Part 3 — The empiricist bet

Part 3

Empiricism makes the opposite wager: all knowledge begins with experience. Nothing is innate. The mind starts empty. This sounds modest, but it leads to some of the most unsettling conclusions in philosophy.

John Locke rejected innate ideas. The mind at birth, he argued, is a tabula rasa — a blank slate. Every idea you have, from the colour red to the concept of justice, entered through experience: sensation (the five senses) and reflection (observing your own mental operations).⁶

This is a structural claim, not a biographical one. Locke is not saying that children must experience everything individually. He is saying that the raw material of all thought comes from experience, and that reason operates on that material but does not generate it from nothing.

graph LR
    E1[Sensation<br/>the five senses] --> M[Mind<br/>blank at birth]
    E2[Reflection<br/>observing your own<br/>mental operations] --> M
    M --> SI[Simple ideas<br/>red, hard, sweet]
    SI --> CI[Complex ideas<br/>justice, causation, substance]

    style M fill:#4a9ede,color:#fff

George Berkeley pushed empiricism into stranger territory. If all knowledge comes from experience, and experience consists of perceptions, then what grounds do you have for believing in a material world behind those perceptions? You never experience matter directly — you experience colours, sounds, textures. Berkeley concluded that to exist is to be perceived (esse est percipi).⁷

Hume’s fork and the problem of induction

David Hume drew out the most severe implication. He divided all knowledge into two categories, now called Hume’s fork:⁸

Category	What it contains	How you know it	Can it be false?
Relations of ideas	Mathematics, logic, definitions	Reason alone	No — denial is a contradiction
Matters of fact	Everything about the world	Experience	Yes — the opposite is conceivable

“2 + 2 = 4” is a relation of ideas — denying it produces a contradiction. “The sun will rise tomorrow” is a matter of fact — you can conceive of it not rising without contradiction. You believe it will rise because it always has. But “it always has” is not a logical guarantee. It is a habit.

This is the problem-of-induction. You observe the sun rising a thousand times and conclude it will rise again. But what justifies the leap from “has always happened” to “will happen”? Not logic — there is no contradiction in the sun failing to rise. Not experience — you cannot experience the future. The justification for induction is… induction. The argument is circular.⁸

Why this matters

Hume did not deny that induction works. He denied that it can be justified. Every empirical generalisation — every law of physics, every medical treatment, every weather forecast — rests on a foundation that cannot prove itself. This is not scepticism as a pose. It is a structural feature of knowledge.

The metaphysical cost

If all knowledge derives from experience, and experience delivers only perceptions, then metaphysics about the ultimate nature of things becomes suspect. You cannot experience causation (only constant conjunction), substance (only bundles of properties), or the self (only a stream of impressions). The empiricist pays for epistemic modesty with metaphysical austerity: reality might be richer than experience, but you have no warrant to say so.⁸

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Part 4 — The synthesis

Part 4

Kant argued that both rationalism and empiricism were half right. The mind does not passively receive experience, and reason alone cannot reach beyond experience. The mind structures experience — and understanding that structure changes everything.

Immanuel Kant read Hume and said it “awakened me from my dogmatic slumber.”⁹ Hume had shown that experience alone cannot ground universal truths. Descartes had shown that reason alone produces an unverifiable metaphysics. Kant’s question was: is there a third option?

His answer: yes, but it requires rethinking the relationship between mind and world.

The Copernican revolution in philosophy

Kant’s insight was an inversion. Previous philosophy assumed that knowledge must conform to objects — that the mind reaches out to grasp a pre-existing reality. Kant proposed the opposite: objects must conform to the structure of the knowing mind. Just as Copernicus solved astronomical problems by making the observer move instead of the sun, Kant solved epistemological problems by making the mind active instead of passive.⁹

graph TD
    subgraph Before[Before Kant]
        W1[World as it is] -->|mind must<br/>conform to| M1[Mind<br/>passive receiver]
    end
    subgraph After[After Kant]
        M2[Mind<br/>active structurer] -->|shapes| E[Experience<br/>the world as<br/>it appears to us]
        R[Reality in itself] -.->|provides raw<br/>material but is<br/>not directly known| E
    end

    style M2 fill:#4a9ede,color:#fff
    style E fill:#5cb85c,color:#fff
    style R fill:#e8b84b,color:#fff

Categories and the analytic-synthetic distinction

Kant argued that the mind comes equipped with categories — not innate ideas (as Descartes claimed), but innate structures that organise raw experience into intelligible form. Space, time, causality, substance, quantity — these are not discovered in the world. They are the lenses through which the mind must process experience. Without them, experience would be a formless stream of impressions.¹⁰

This led to the analytic-synthetic-distinction, which restructured the entire debate:¹⁰

Type	Definition	Example
Analytic	The predicate is contained in the subject	”All bachelors are unmarried”
Synthetic	The predicate adds something new	”The cat is on the mat”
A priori	Known independently of experience	”7 + 5 = 12”
A posteriori	Known through experience	”Water boils at 100C”

The revolutionary move: Kant argued that synthetic a priori knowledge exists. “7 + 5 = 12” is synthetic (the concept of 12 is not contained in the concepts of 7, 5, and addition) and a priori (you do not need to count physical objects to know it). This category is what makes science possible — universal truths about the world that are not mere definitions.¹⁰

Phenomena and noumena

The price of Kant’s synthesis is a permanent boundary. If the mind structures all experience, then you never experience reality as it is in itself. You only experience reality as structured by your cognitive apparatus.

Kant called the world as experienced phenomena (appearances) and the world as it is in itself noumena (things-in-themselves). We have access to phenomena. Noumena are thinkable but unknowable.¹¹

graph LR
    N[Noumena<br/>things in themselves<br/>unknowable] -->|filtered through<br/>categories of the mind| P[Phenomena<br/>things as they<br/>appear to us<br/>knowable]

    style N fill:#e8b84b,color:#fff
    style P fill:#5cb85c,color:#fff

Why this matters

Kant did not split the world in two arbitrarily. He showed that every claim to knowledge already presupposes a knowing mind with a specific structure. You cannot step outside your own cognition to check whether it matches reality. This is not a failure of knowledge — it is its condition of possibility. The limits of knowledge and the structure of knowledge are the same thing.

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Part 5 — Logic as infrastructure

Part 5

Epistemology asks what we can know. Metaphysics asks what is real. Logic asks a different question entirely: what follows from what? It is the infrastructure underneath both, and confusing it with either produces errors that cascade through everything.

Every philosophical argument in this path — Descartes’ cogito, Hume’s problem of induction, Kant’s categories — has a logical structure. The conclusions hold (or fail) based on whether the reasoning is valid. But what does “valid” mean, and how does it relate to truth?

Validity is not truth

A deductive argument is valid if the conclusion follows necessarily from the premises. The premises can be false and the argument still valid:¹²

All fish can fly. (false) Salmon are fish. (true) Therefore, salmon can fly. (false, but validly derived)

An argument is sound if it is valid and all its premises are true. Logic guarantees the preservation of truth through valid inference. It does not guarantee the truth of your starting points. That is epistemology’s job.

graph TD
    V{Valid?<br/>Does the conclusion<br/>follow from premises?}
    V -->|Yes| S{Sound?<br/>Are the premises<br/>also true?}
    V -->|No| F[Fallacy<br/>conclusion does<br/>not follow]
    S -->|Yes| K[Knowledge<br/>candidate]
    S -->|No| VF[Valid but false<br/>the reasoning works<br/>the inputs are wrong]

    style K fill:#5cb85c,color:#fff
    style F fill:#e74c3c,color:#fff
    style VF fill:#e8b84b,color:#fff

Three modes of inference

Philosophy and science rely on three fundamentally different types of reasoning, each with different strengths:¹²¹³

Mode	Direction	Strength	Risk
Deduction	General to particular	If premises are true, conclusion is guaranteed	Only unpacks what the premises already contain
Induction	Particular to general	Generates new generalisations from observed cases	Hume’s problem: no logical guarantee
Abduction	Effect to best explanation	Generates hypotheses and explanations	The “best” explanation might be wrong

Deduction is truth-preserving but cannot generate new knowledge about the world. Every deductive conclusion is already implicit in the premises.

Induction generates new claims (“all observed swans are white, therefore all swans are white”) but cannot guarantee them.

Abduction is how most actual reasoning works: you observe a wet street and infer it rained. You observe symptoms and infer a diagnosis. Peirce called it “the only logical operation which introduces any new idea.”¹³ It is also the least secure — there might always be a better explanation you have not considered.

Why logic is not separable from epistemology

Notice the dependency: deduction preserves truth but needs true premises (epistemology’s problem). Induction generates knowledge but cannot justify itself (Hume’s problem). Abduction explains but cannot prove. Each mode of inference exposes a different gap in how we know, and each gap is an epistemological question wearing logical clothes.

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Part 6 — Metaphysics as constraint

Part 6

Your epistemology — how you think knowledge works — quietly forces a position on what reality must be like. Metaphysics is not a separate elective. It is the consequence of your epistemic commitments.

The central question of metaphysics is: what exists, and what is it like? But this question is not independent of epistemology. What you think you can know constrains what you can coherently claim is. The major positions form a spectrum, and your location on it follows from the bets made in Parts 2-4.

The realism-idealism spectrum

graph LR
    R[Realism<br/>reality exists<br/>independently of mind] --- TI[Transcendental<br/>Idealism<br/>reality exists but<br/>is filtered by mind]
    TI --- SI[Subjective<br/>Idealism<br/>only perceptions<br/>exist]

    style R fill:#4a9ede,color:#fff
    style TI fill:#e8b84b,color:#fff
    style SI fill:#9b59b6,color:#fff

Position	Core claim	Epistemological commitment	Who holds it
Realism	The world exists independently of any mind	We can know the world as it is (or approximately)	Most working scientists, Aristotle
Transcendental idealism	Reality exists but is shaped by the mind’s categories	We know phenomena, not things-in-themselves	Kant
Subjective idealism	Only perceptions exist; matter is a construction	All knowledge is of mental states	Berkeley

The problem of universals

A different axis cuts across the realism-idealism spectrum. When you say “this ball is red” and “that car is red,” is there a single thing — redness — that both objects share? Or is “red” just a label you apply to things that look similar?

This is the problem of universals, and the three classical answers reveal deep metaphysical commitments:¹⁴¹⁵

Position	Answer	Consequence
Platonic realism	Universals exist independently of particular things — redness exists in a realm of Forms	Commits you to abstract objects and a non-physical realm of reality
Aristotelian realism	Universals exist but only in particular things — redness exists in red objects	Reality is richer than the physical but not separate from it
Nominalism	Universals do not exist — “redness” is a word we use for a family resemblance	Only particular, concrete things exist

The dependency

Your metaphysics constrains your epistemology and vice versa. A nominalist who denies universals cannot appeal to them when explaining how knowledge generalises. A Platonic realist who posits abstract forms must explain how a physical mind accesses a non-physical realm. Each position solves one problem by creating another. This is not a design flaw in philosophy. It is the structure of the problem.

Substance and the mind-body problem

Descartes’ two-substance metaphysics (mind and matter) created a problem that philosophy still has not solved: if mind and body are fundamentally different kinds of stuff, how do they interact? How does a non-physical thought cause a physical arm to move?

This is not a historical curiosity. Every position on the mind-body problem carries epistemological weight:

• Dualism: mind and body are separate. Problem: how do they interact?
• Physicalism: everything is physical, including mind. Problem: how does subjective experience arise from matter?
• Neutral monism: neither mind nor matter is fundamental — both are manifestations of something deeper. Problem: what is that something?

Each answer constrains what kind of knowledge is possible and what kind of reality knowledge is about.

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Part 7 — The modern fracture

Part 7

After Kant, philosophy fractured into traditions that reframed the classical questions rather than answering them within the old framework. Three of these fractures matter most.

Pragmatism: redefine truth

Pragmatism, born in 1870s Cambridge (Massachusetts) from conversations between Charles Sanders Peirce and William James, rejected the question “does this belief correspond to reality?” and replaced it with “what difference does holding this belief make?”¹⁶

Peirce framed it as a method: to clarify the meaning of any concept, trace out the practical consequences of its being true. If two propositions have identical practical consequences, they mean the same thing regardless of how different they sound in theory.¹⁶

James applied this to truth itself: a true belief is one that “works” — that successfully guides action and prediction. This is not relativism (“truth is whatever you want”). It is operationalism: truth is not a static correspondence between proposition and world but a dynamic relationship between belief and consequence.¹⁶

John Dewey extended pragmatism into a theory of inquiry: knowledge is not the mind mirroring nature but the organism solving problems. Thinking is an activity, not a representation.¹⁶

Phenomenology: return to experience

Edmund Husserl argued that philosophy had become lost in abstractions. Both rationalists and empiricists had theories about experience without examining experience itself. His programme, phenomenology, was to describe the structures of consciousness as they present themselves, before any theoretical overlay.¹⁷

The central concept is intentionality: every mental act is directed at something. You do not just “think” — you think about something. Consciousness is always consciousness of. This is not a trivial observation. It means that the subject-object split assumed by both rationalism and empiricism is already a theoretical imposition on something more fundamental: the directedness of experience.¹⁷

Heidegger radicalised this. He argued that Husserl still thought of consciousness as something detached from the world. For Heidegger, we are always already in the world — our being is being-in-the-world (Dasein). The question is not “how does a mind access a world?” but “what is the being that asks questions about being?”¹⁸

Analytic philosophy: clarify the language

Bertrand Russell, Gottlob Frege, and the early Ludwig Wittgenstein argued that many philosophical problems are not problems about reality but problems about language. When we ask “does the mind exist?” we might be confusing ourselves with a grammatically misleading sentence rather than probing a genuine metaphysical question.

The later Wittgenstein went further: meaning is use. Words do not get their meaning by corresponding to objects in the world. They get their meaning from how they are used within “language games” — rule-governed social practices. Philosophy’s task is not to discover truths about reality but to dissolve confusions generated by the misuse of language.

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The map so far

graph TD
    EP[Epistemology<br/>What can we know?] --> R[Rationalism<br/>reason first]
    EP --> EM[Empiricism<br/>experience first]
    R --> KS[Kant<br/>mind structures<br/>experience]
    EM --> KS
    KS --> MOD[Modern fracture]

    L[Logic<br/>What follows from what?] --> DED[Deduction<br/>truth-preserving]
    L --> IND[Induction<br/>generalising]
    L --> ABD[Abduction<br/>explaining]

    MT[Metaphysics<br/>What is real?] --> REA[Realism]
    MT --> IDE[Idealism]
    MT --> NOM[Nominalism]

    EP <-->|constrains| MT
    L <-->|grounds| EP
    MT <-->|requires| L

    MOD --> PR[Pragmatism<br/>truth is what works]
    MOD --> PH[Phenomenology<br/>return to experience]
    MOD --> AN[Analytic philosophy<br/>clarify the language]

    style EP fill:#4a9ede,color:#fff
    style L fill:#5cb85c,color:#fff
    style MT fill:#e8b84b,color:#fff

The three disciplines form a triangle, not a stack. You cannot do epistemology without logical inference. You cannot do logic without metaphysical commitments about what “truth” and “existence” mean. You cannot do metaphysics without epistemological assumptions about what you can know. Pull any corner, the other two move.

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What you now understand

Concepts you have gained

• Justified-true-belief — the classical definition of knowledge and why it fails (Gettier)
• Rationalism — the bet that reason can reach truths about reality independently of experience
• Empiricism — the bet that all knowledge begins with experience, and its consequences (problem of induction)
• Analytic-synthetic-distinction — Kant’s framework for categorising types of knowledge
• Phenomena-noumena — the boundary between the world as experienced and the world as it is
• Deduction, induction, abduction — three modes of inference with different strengths and risks
• Realism, idealism, nominalism — the spectrum of metaphysical positions and their epistemological costs
• Pragmatism — truth as what works, not what corresponds
• Phenomenology — the return to the structure of experience before theory

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Check your understanding

Test yourself before moving on (click to expand)

1. Explain why the Gettier problem cannot be fixed by simply “being more careful” with justification. What structural feature of the JTB account does it expose?
2. Compare the metaphysical costs of rationalism and empiricism. What does each tradition commit you to believing about the nature of reality?
3. Interpret Kant’s claim that “objects must conform to the mind” rather than the reverse. What problem does this solve, and what new problem does it create?
4. Distinguish deduction, induction, and abduction using a single scenario (for example: a doctor diagnosing a patient). Which mode applies at each stage of reasoning?
5. Evaluate the pragmatist redefinition of truth. If truth is “what works,” what happens when two contradictory beliefs both work in different contexts? Does pragmatism have an answer to this, or is it a genuine weakness?

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Where to go next

Path A: Knowledge representation

You have the philosophical substrate. Now see how these questions play out in the design of AI knowledge systems — how machines represent, store, and reason about knowledge. Read knowledge-epistemology.

Best for: Builders who want to connect philosophical foundations to practical AI/knowledge system design.

Path B: Deep dive into a single tradition

Pick the tradition that resonated most — rationalism, empiricism, Kant, pragmatism, or phenomenology — and read the primary texts with the structural framework from this path as your map.

Best for: Readers who want depth over breadth and are ready for primary sources.

Path C: Logic and formal reasoning

Explore formal logic in depth — propositional logic, predicate logic, modal logic — and how logical systems underpin scientific reasoning and argument analysis.

Best for: Readers drawn to the structural, mathematical side of philosophy.

Path D: Philosophy of science

Apply these foundations to the specific question of scientific knowledge: what makes a theory scientific, how paradigms shift, and why falsifiability matters.

Best for: Readers interested in how philosophy grounds (and sometimes undermines) scientific method.

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Sources

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Further reading

Resources

• Nagel, J. Knowledge: A Very Short Introduction — The best short entry point to epistemology; accessible without being shallow
• Blackburn, S. Think: A Compelling Introduction to Philosophy — Covers epistemology, metaphysics, and logic in a single coherent narrative
• Descartes, R. Meditations on First Philosophy — The primary text for rationalism; short, readable, and still provocative after 400 years
• Hume, D. An Enquiry Concerning Human Understanding — The primary text for empiricism; clearer than the Treatise and more focused
• Kant, I. Prolegomena to Any Future Metaphysics — Kant’s own condensed summary of the Critique of Pure Reason; start here, not the Critique
• Philosophy Break: Epistemology Reading List — Curated nine-book reading list from introductory to advanced

Footnotes

1. Steup, M. & Neta, R. Epistemology. Stanford Encyclopedia of Philosophy. ↩

2. Gettier, E. (1963). “Is Justified True Belief Knowledge?” Analysis, 23(6), 121-123. ↩

3. Hetherington, S. Gettier Problems. Internet Encyclopedia of Philosophy. ↩

4. Ichikawa, J. & Steup, M. The Analysis of Knowledge. Stanford Encyclopedia of Philosophy. ↩

5. Descartes, R. (1641). Meditations on First Philosophy. Translated by J. Cottingham (1996). Cambridge University Press. ↩ ↩² ↩³

6. Markie, P. & Folescu, M. Rationalism vs. Empiricism. Stanford Encyclopedia of Philosophy. ↩ ↩² ↩³

7. Downing, L. George Berkeley. Stanford Encyclopedia of Philosophy. ↩

8. Hume, D. (1748). An Enquiry Concerning Human Understanding. Edited by T. Beauchamp (1999). Oxford University Press. ↩ ↩² ↩³

9. Rohlf, M. Immanuel Kant. Stanford Encyclopedia of Philosophy. ↩ ↩²

10. Willaschek, M. & Watkins, E. Kant’s Critique of Metaphysics. Stanford Encyclopedia of Philosophy. ↩ ↩² ↩³

11. Stang, N. Kant’s Transcendental Idealism. Stanford Encyclopedia of Philosophy. ↩

12. Smith, R. Aristotle’s Logic. Stanford Encyclopedia of Philosophy. ↩ ↩²

13. Douven, I. Abduction. Stanford Encyclopedia of Philosophy. ↩ ↩²

14. Rodriguez-Pereyra, G. Nominalism in Metaphysics. Stanford Encyclopedia of Philosophy. ↩

15. Miller, A. Realism. Stanford Encyclopedia of Philosophy. ↩

16. Legg, C. & Hookway, C. Pragmatism. Stanford Encyclopedia of Philosophy. ↩ ↩² ↩³ ↩⁴

17. Smith, D.W. Phenomenology. Stanford Encyclopedia of Philosophy. ↩ ↩²

18. Wheeler, M. Martin Heidegger. Stanford Encyclopedia of Philosophy. ↩