1001Philosophers

John Locke vs Rene Descartes on Knowledge

Descartes builds knowledge a priori from the cogito, treating clear and distinct ideas as the criterion of certainty. Locke builds knowledge a posteriori from the materials of sensation and reflection, with experience as the only source of substantive content. The Cartesian and Lockean accounts of knowing frame the rationalist-empiricist division that structures all of early modern epistemology.

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 John Locke vs Rene Descartes comparison. To browse philosophy more widely on this theme, see the Knowledge quotes hub.

Representative quotes on knowledge

John Locke on knowledge

  • “No man's knowledge here can go beyond his experience.”

    Book II, Ch. 1, sec. 19

  • “Reading furnishes the mind only with materials of knowledge; it is thinking that makes what we read ours.”

    As quoted in "Hand Book : Caution and Counsels" in The Common School Journal Vol. 5, No. 24 (15 December 1843) by Horace Mann , p. 371

  • “It is one thing to show a man that he is in error, and another to put him in possession of truth.”

    Book IV, Ch. 7, sec. 11

  • “There is frequently more to be learned from the unexpected questions of a child than the discourses of men.”

    Sec. 121

  • “New opinions are always suspected, and usually opposed, without any other reason but because they are not common.”

    Dedicatory epistle, as quoted in Fred R Shapiro (2006). The Yale Book of Quotations . Yale University Press. p. 468. ISBN 0-300-10798-6 .

All 13 John Locke 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)

  • “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 (1637) as quoted by D. E. Smith & M. L. Latham Tr. The Geometry of René Descartes (1925)”

    What I have given in the second book on the nature and properties of curved lines, and the method of examining them, is, it seems to me, as far beyond the treatment in the ordinary geometry, as the rhetoric of Cicero is beyond the a, b, c of children.

All 13 Rene Descartes quotes on knowledge →

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