Principles of Philosophy

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Principles of Philosophy

work by Descartes

Also known as: “Principia Philosophiae”

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June 11, 2026

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René Descartes's Principles of Philosophy is a foundational work in modern philosophy, emphasizing a rationalist approach to knowledge. Descartes employed a method of methodic doubt to systematically question all beliefs, seeking indubitable truths. This process led him to the famous dictum "cogito, ergo sum" ("I think, therefore I am"), asserting that the act of thinking proves one's own existence.123456

From this certainty, Descartes aimed to establish a foundation for knowledge, including the existence of God and the material world, through clear and distinct ideas. His philosophy introduced a dualism between mind and matter, influencing subsequent philosophical and scientific thought.715

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cogito, ergo sum
…in a later work, the Principles of Philosophy (1644), Descartes suggested that the cogito is indeed the conclusion of a syllogism whose premises include the propositions that he is thinking and that whatever thinks must exist.
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…in a later work, the Principles of Philosophy (1644), Descartes suggested that the cogito is indeed the conclusion of a syllogism whose premises include the propositions that he is thinking and that whatever thinks must exist.
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René Descartes
Physics, physiology, and morals
In 1644 Descartes published Principles of Philosophy, a compilation of his physics and metaphysics. He dedicated this work to Princess Elizabeth (1618–79), daughter of Elizabeth Stuart, titular queen of Bohemia, in correspondence with whom he developed his moral philosophy. According to Descartes, a human being is a union of…
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In 1644 Descartes published Principles of Philosophy, a compilation of his physics and metaphysics. He dedicated this work to Princess Elizabeth (1618–79), daughter of Elizabeth Stuart, titular queen of Bohemia, in correspondence with whom he developed his moral philosophy. According to Descartes, a human being is a union of…
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Benedict de Spinoza
Rijnsburg and The Hague
…of Descartes’s Principia Philosophiae (1644; Principles of Philosophy), it showed a profound understanding of Descartes’s system. Although Spinoza generally accepted Descartes’s physics, he rejected Cartesian metaphysics, objecting to three features: the transcendence of God, the conception of mind as a “mental substance” radically distinct from matter (see mind-body dualism),
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…of Descartes’s Principia Philosophiae (1644; Principles of Philosophy), it showed a profound understanding of Descartes’s system. Although Spinoza generally accepted Descartes’s physics, he rejected Cartesian metaphysics, objecting to three features: the transcendence of God, the conception of mind as a “mental substance” radically distinct from matter (see mind-body dualism),
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Western philosophy
The rationalism of Descartes
…of human action in the Principles of Philosophy (1644) and The Passions of the Soul (1649), and a mathematical bias that dominates the theory of method in Rules for the Direction of the Mind (1701) and the metaphysics of the Meditations on the First Philosophy (1642). But it is the…
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…of human action in the Principles of Philosophy (1644) and The Passions of the Soul (1649), and a mathematical bias that dominates the theory of method in Rules for the Direction of the Mind (1701) and the metaphysics of the Meditations on the First Philosophy (1642). But it is the…
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