1001Philosophers

Plato vs Rene Descartes on Knowledge

For Plato, knowledge is the soul's recovery of the Forms it knew before embodiment — a return to what is already possessed. For Descartes, knowledge begins with the cogito and proceeds by careful reasoning from indubitable foundations; nothing is recollected, everything is reconstructed. The shift from Platonic anamnesis to Cartesian foundationalism marks the modern conception of the autonomous knowing subject.

About this topic

Epistemology is the branch of philosophy concerned with the nature, sources, and limits of knowledge. Philosophers have asked what distinguishes knowledge from mere opinion, whether it requires certainty or can be probabilistic, and how perception, reason, memory, and testimony each contribute. Ancient skeptics challenged the possibility of knowledge altogether, while rationalists located its source in reason and empiricists in experience. Contemporary epistemology investigates justification, reliability, and the social conditions under which beliefs count as knowing.

For a side-by-side overview of the two philosophers more broadly, see the full Plato vs Rene Descartes comparison. To browse philosophy more widely on this theme, see the Knowledge quotes hub.

Representative quotes on knowledge

Plato on knowledge

  • “Philosophy begins in wonder.”

    155d, The Dialogues of Plato , Volume 3, 1871, p. 377

  • “I shall assume that your silence gives consent .”

    435b

  • “If the very essence of knowledge changes, at the moment of the change to another essence of knowledge there would be no knowledge, and if it is always changing, there will always be no knowledge, and by this reasoning there will be neither anyone to know nor anything to be known. But if there is always that which knows and that which is known —if the beautiful, the good, and all the other verities exist— I do not see how there is any likeness between these conditions of which I am now speaking and flux or motion.”

    440a–b

  • “Wonder is the feeling of a philosopher, and philosophy begins in wonder.”

    155d, The Dialogues of Plato , Volume 3, 1871, p. 377

  • “Perception and knowledge could never be the same.”

    186e

All 12 Plato quotes on knowledge →

Rene Descartes on knowledge

  • “I think, therefore I am.”

    Je pense, donc je suis.

  • “If you would be a real seeker after truth, it is necessary that at least once in your life you doubt, as far as possible, all things.”

    In order to seek truth, it is necessary once in the course of our life, to doubt, as far as possible, of all things.

  • “No doubt you know that Galileo had been convicted not long ago by the Inquisition, and that his opinion on the movement of the Earth had been condemned as heresy. Now I will tell you that all things I explain in my treatise , among which is also that same opinion about the movement of the Earth, all depend on one another, and are based upon certain evident truths. Nevertheless, I will not for the world stand up against the authority of the Church. ...I have the desire to live in peace and to continue on the road on which I have started.”

    Letter to Marin Mersenne (end of Feb., 1634) as quoted by Amir Aczel , Pendulum: Leon Foucault and the Triumph of Science (2003)

  • “No doubt you know that Galileo had been convicted not long ago by the Inquisition, and that his opinion on the movement of the Earth had been condemned as heresy. Now I will tell you that all things I explain in my treatise , among which is also that same opinion about the movement of the Earth, all depend on one another, and are based upon certain evident truths. Nevertheless, I will not for the ”

    Letter to Marin Mersenne (end of Feb., 1634) as quoted by Amir Aczel , Pendulum: Leon Foucault and the Triumph of Science (2003)

  • “M. Desargues puts me under obligations on account of the pains that it has pleased him to have in me, in that he shows that he is sorry that I do not wish to study more in geometry, but I have resolved to quit only abstract geometry, that is to say, the consideration of questions which serve only to exercise the mind , and this, in order to study another kind of geometry, which has for its object the explanation of the phenomena of nature... You know that all my physics is nothing else than geometry.”

    Letter to Marin Mersenne (July 27, 1638) as quoted by Florian Cajori , A History of Mathematics (1893) letter dated in The Philosophical Writings of Descartes Vol. 3, The Correspondence (1991) ed. John Cottingham, Robert Stoothoff, Dugald Murdoch

All 11 Rene Descartes quotes on knowledge →

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