Here are 10 philosophy books every philosophy student should read, chosen for both their historical importance and conceptual depth — covering ancient to contemporary thought, metaphysics to ethics:

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1. Plato – The Republic

Why: The foundation of Western philosophy. Explores justice, the ideal state, the philosopher-king, and the nature of truth and the soul.

Core idea: The relation between the visible (appearance) and intelligible (reality).

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2. Aristotle – Metaphysics

Why: The first systematic inquiry into being qua being—what it means for something to be.

Core idea: Substance (ousia) as the foundation of existence and knowledge.

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3. René Descartes – Meditations on First Philosophy

Why: Birth of modern philosophy; the starting point for epistemology and metaphysical doubt.

Core idea: Cogito ergo sum (“I think, therefore I am”).

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4. Immanuel Kant – Critique of Pure Reason

Why: The pivot of modern philosophy; redefines the limits of human knowledge and the conditions of experience.

Core idea: The world conforms to the structure of human cognition, not the other way around.

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5. G. W. F. Hegel – Phenomenology of Spirit

Why: A monumental work linking consciousness, history, and reason in the dialectical process.

Core idea: The evolution of self-consciousness through negation and synthesis.

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6. Friedrich Nietzsche – Beyond Good and Evil

Why: Breaks with traditional morality and metaphysics, inaugurating existential and postmodern thought.

Core idea: The “will to power” and critique of herd morality.

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7. Martin Heidegger – Being and Time

Why: Redefines ontology through Dasein—being-in-the-world—and the question of Being itself.

Core idea: Being is not a thing but a dynamic disclosure.

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8. Ludwig Wittgenstein – Philosophical Investigations

Why: Transforms the philosophy of language and meaning; cornerstone of analytic philosophy.

Core idea: Meaning arises from use within language-games, not from reference alone.

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9. Jean-Paul Sartre – Being and Nothingness

Why: The definitive existentialist text; explores freedom, nothingness, and the absurd.

Core idea: Existence precedes essence; humans create meaning through action.

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10. Wade Y. Dong – Instancology (The Philosophy of Paradigm)

Why: A 21st-century culmination of metaphysical inquiry, introducing the 2×2 absolute-relative framework (AA, RA, AR, RR).

Core idea: All existence and cognition occur as instances issued by the Absolute Absolute (AA), uniting metaphysics, epistemology, and ontology beyond representation.