René Descartes (1596–1650) was a French philosopher, mathematician, and man of science. Often called the father of modern philosophy, Descartes rejected Aristotle’s proposal that knowledge is derived from the senses and promoted a ‘new science’ grounded in reason, observation, and experiment.
Born in La Haye, Touraine, Descartes introduced the notion of universal doubt. Aiming to reach secure foundations for knowledge, he began by attacking all his beliefs with skeptical doubts and considered all that was certain was his consciousness and therefore existence. This is summed up in his famous phrase, “Cogito ergo sum” (“l think, therefore I am.”)
Descartes founded the rationalist school of philosophy known as Cartesianism. He also founded analytic geometry, introduced the Cartesian coordinate system, and helped establish the science of optics. Descartes’s analytic geometry laid the groundwork of the calculus developed by Isaac Newton and Gottfried Wilhelm Leibniz.
Descartes also developed a metaphysical dualism that distinguishes radically between mind, the essence of which is, feeling, and reasoning, and matter, which is a physical entity that conforms to the laws of physics—like a machine.
Descartes expounded on his mathematical theories in his famous Discours de la Méthode (1637; Discourse on Method.) His notable works on philosophy include Meditationes de Prima Philosophia (1641; Meditations on the First Philosophy) and Principia Philosophiæ (1644; Principles of Philosophy.) Descartes’s methods of deduction and intuition enlighten modern metaphysics.
Descartes’s other philosophical works include Regufae ad directionem ingenii (Rules for the Direction of the Mind, composed in the 1620s, but unfinished and published posthumously in 1701) and Les Passions de f’ame (1649; Passions of the Soul.)
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I think therefore I am.
—Rene Descartes
Let us suppose, then, that we are dreaming, and that all these particulars—namely, the opening of the eyes, the motion of the head, the forth- putting of the hands—are merely illusions; and even that we really possess neither an entire body nor hands such as we see. Nevertheless it must be admitted at least that the objects which appear to us in sleep are, as it were, painted representations which could not have been formed unless in the likeness of realities; and, therefore, that those general objects, at all events, namely, eyes, a head, hands, and an entire body, are not simply imaginary, but really existent. For, in truth, painters themselves, even when they study to represent sirens and satyrs by forms the most fantastic and extraordinary, cannot bestow upon them natures absolutely new, but can only make a certain medley of the members of different animals; or if they chance to imagine something so novel that nothing at all similar has ever been seen before, and such as is, therefore, purely fictitious and absolutely false, it is at least certain that the colors of which this is composed are real. And on the same principle, although these general objects, viz. a body, eyes, a head, hands, and the like, be imaginary, we are nevertheless absolutely necessitated to admit the reality at least of some other objects still more simple and universal than these, of which, just as of certain real colors, all those images of things, whether true and real, or false and fantastic, that are found in our consciousness (cogitatio), are formed.
—Rene Descartes
Topics: Reality
Thinking is another attribute of the soul; and here I discover what properly belongs to myself. This alone is inseparable from me. I am—I exist: this is certain; but how often? As often as I think; for perhaps it would even happen, if I should wholly cease to think, that I should at the same time altogether cease to be. I now admit nothing that is not necessarily true: I am therefore, precisely speaking, only a thinking thing, that is, a mind, understanding, or reason,—terms whose signification was before unknown to me. I am, however, a real thing, and really existent; but what thing? The answer was, a thinking thing. The question now arises, am I aught besides? I will stimulate my imagination with a view to discover whether I am not still something more than a thinking being. Now it is plain I am not the assemblage of members called the human body; I am not a thin and penetrating air diffused through all these members, or wind, or flame, or vapour, or breath, or any of all the things I can imagine; for I supposed that all these were not, and, without changing the supposition, I find that I still feel assured of my existence.
—Rene Descartes
Topics: Thought
Nothing is more fairly distributed than common sense: no one thinks he needs more of it than he already has.
—Rene Descartes
Topics: Common Sense, Common Sense
Except our own thoughts, there is nothing absolutely in our power.
—Rene Descartes
Topics: Thinking, Thoughts, Thought
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.
—Rene Descartes
Topics: Doubt
Each problem that I solved became a rule which served afterwards to solve other problems.
—Rene Descartes
Topics: Problems, Rationality, Knowledge, War
Thus even in the very example my critics produce, it is the intellect alone which corrects the error of the senses; and it is not possible to produce any case which error results from our trusting the operation of the mind more than the senses.
—Rene Descartes
Everything is self-evident.
—Rene Descartes
Topics: Reality
In order to improve the mind, we ought less to learn, than to contemplate.
—Rene Descartes
Topics: Wisdom, Think
When any one has offended me, I try to raise my soul so high that the offense cannot reach it.
—Rene Descartes
Topics: Insults, Meditation
It is only prudent never to place complete confidence in that by which we have even once been deceived.
—Rene Descartes
Topics: Confidence
When writing about transcendental issues, be transcendentally clear.
—Rene Descartes
Topics: Authors & Writing
The chief cause of human errors is to be found in prejudices picked up in childhood.
—Rene Descartes
It is well to know something of the manners of various peoples, in order more sanely to judge our own, and that we do not think that everything against our modes is ridiculous, and against reason, as those who have seen nothing are accustomed to think.
—Rene Descartes
Topics: Equality
To know what people really think, pay regard to what they do, rather than what they say.
—Rene Descartes
Topics: Behavior, Manners
There may indeed be those who would prefer to deny the existence of a God so powerful, rather than believe that all other things are uncertain. But let us not oppose them for the present, and grant that all that is here said of a God is a fable; nevertheless in whatever way they suppose that I have arrived at the state of being that I have reached—whether they attribute it to fate or to accident, or make out that it is by a continual succession of antecedents, or by some other method—since to err and deceive oneself is a defect, it is clear that the greater will be the probability of my being so imperfect as to deceive myself ever, as is the Author to whom they assign my origin the less powerful. To these reasons I have certainly nothing to reply, but at the end I feel constrained to confess that there is nothing in all that I formerly believed to be true, of which I cannot in some measure doubt, and that not merely through want of thought or through levity, but for reasons which are very powerful and maturely considered; so that henceforth I ought not the less carefully to refrain from giving credence to these opinions than to that which is manifestly false, if I desire to arrive at any certainty in the sciences.
—Rene Descartes
Topics: Belief
I hope that posterity will judge me kindly, not only as to the things which I have explained, but also to those which I have intentionally omitted so as to leave to others the pleasure of discovery.
—Rene Descartes
Topics: Legacy
It is not enough to have a good mind. The main thing is to use it well.
—Rene Descartes
Topics: Mind, Letters, Thinking, Love
One cannot conceive anything so strange and so implausible that it has not already been said by one philosopher or another.
—Rene Descartes
Topics: Philosophers, Oddity, Peculiarity, Philosophy
Divide each difficulty into as many parts as is feasible and necessary to resolve it.
—Rene Descartes
Topics: Difficulty, Simplicity
We never understand a thing so well, and make it our own, as when we have discovered it for ourselves.
—Rene Descartes
Topics: Self-Discovery
The only secure knowledge is that I exist
—Rene Descartes
Topics: One liners, Philosophy
I am accustomed to sleep, and in my dreams to imagine the same things that lunatics imagine when awake.
—Rene Descartes
Topics: Sleep, Dreams
The reading of all good books is indeed like a conversation with the noblest men of past centuries who were the authors of them, nay a carefully studied conversation, in which they reveal to us none but the best of their thoughts.
—Rene Descartes
Topics: Wisdom, Reading, Learning
Illusory joy is often worth more than genuine sorrow.
—Rene Descartes
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