René Descartes' "Meditations on First Philosophy" argues that the existence of the thinking self ("Cogito, ergo sum" - I think, therefore I am) is the only absolutely certain truth, serving as the foundation for all other knowledge. He establishes this by employing radical doubt, questioning sensory experience, mathematical truths, and even the physical world's existence, acknowledging the possibility of an "evil demon" deceiver. From this foundational certainty, Descartes distinguishes the non-material thinking substance (mind) from the material extended substance (body), introducing mind-body dualism.
Through six meditations, Descartes builds upon this foundation to prove the existence of God, first by positing that the idea of a perfect being must originate from God himself, and second through the ontological argument that existence is part of God's perfection. He explains errors as the misuse of free will and ultimately concludes that the external world and material objects exist, guaranteed by a non-deceiving God, thus providing a secure basis for scientific and philosophical knowledge.
Key concepts
- Cogito, ergo sum — The indubitable truth that the act of thinking proves one's own existence.
- Evil demon — A hypothetical deceiver whose existence is considered to explore radical doubt.
- Mind-body dualism — The distinction between the non-material thinking substance (mind) and the material extended substance (body).
- Argument for the existence of God — Descartes' reasoning that the idea of perfection implies the existence of a perfect being (God).
- Ontological argument — An argument for God's existence based on the concept of a perfect being necessarily possessing existence.
- Radical doubt — A method of systematically questioning all beliefs to find absolute certainty.