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René Descartes (1596–1650) French philosopher, mathematician, and scientist

“Conquer yourself rather than the world.”

René Descartes (1596–1650) French philosopher, mathematician, and scientist

“Common sense is the most widely shared commodity in the world, for every man is convinced that he is well supplied with it.”

René Descartes (1596–1650) French philosopher, mathematician, and scientist

“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.”

René Descartes book Principles of Philosophy

Original Latin: Veritatem inquirenti, semel in vita de omnibus, quantum fieri potest, esse dubitandum
Variant translation: If you would be a real seeker after truth, you must at least once in your life doubt, as far as possible, all things.
Principles of Philosophy (1644)
Variant: In order to seek truth, it is necessary once in the course of our life, to doubt, as far as possible, of all things.

“I think, therefore I am.”

René Descartes (1596–1650) French philosopher, mathematician, and scientist

Je pense, donc je suis.
Le Discours de la Méthode (1637)
Variant: I think, therefore I am.

“Except our own thoughts, there is nothing absolutely in our power.”

René Descartes (1596–1650) French philosopher, mathematician, and scientist

“My third maxim was to endeavor always to conquer myself rather than fortune, and change my desires rather than the order of the world.”

René Descartes book Discurso sobre o Método

Source: Discourse on Method (Rozprava o metodě)

“Mr. Clerselier has written me that you are expecting from him my Meditations… in order to present them to the queen of the land. …If I had only been as wise as they say the savages persuaded themselves that the monkeys were, I never would have become known as a maker of books: Since it is said that they imagined that the monkeys could indeed speak, if they wanted to, but that they chose not to so lest they be forced to work. And since I had not the same prudence to abstain from writing, I now have neither as much liesure nor as much peace as I would have had if I had kept quiet. But since the mistake has already been made, and since I am now known by an infinity of people at the academy, who look askance at my writings and scour them for means of harming me, I do have great hope of being known to persons of great merit, whose power and virtue could protect me.”

René Descartes (1596–1650) French philosopher, mathematician, and scientist

Letter to Pierre Chanut (Nov. 1, 1646) as quoted by Amir Aczel, Descartes' Secret Notebook (2005) citing René Descartes: Correspondance avec Elizabeth et autres lettres (1989) ed., Jean-Marie and M. Beysaade, pp. 245-246.

“The entire method consists in the order and arrangement of the things to which the mind’s eye must turn so that we can discover some truth.”

René Descartes book Rules for the Direction of the Mind

Rules for the Direction of the Mind: X.379
As quoted in [Clarke, Desmond M., 2006, Descartes : a Biography, Cambridge Press, 67, ISBN 978-0-521-82301-2]

“It is not enough to have a good mind. The main thing is to use it well.”

René Descartes (1596–1650) French philosopher, mathematician, and scientist

Variant: It is not enough to have a good mind; the main thing is to use it well.
Source: Discourse on Method

“Divide each difficulty into as many parts as is feasible and necessary to resolve it.”

René Descartes (1596–1650) French philosopher, mathematician, and scientist

Source: Discourse on Method

“There is nothing more ancient than the truth.”

René Descartes (1596–1650) French philosopher, mathematician, and scientist

“But in my opinion, all things in nature occur mathematically.”

René Descartes (1596–1650) French philosopher, mathematician, and scientist

“And thus, the actions of life often not allowing any delay, it is a truth very certain that, when it is not in our power to determine the most true opinions we ought to follow the most probable.”

René Descartes (1596–1650) French philosopher, mathematician, and scientist