“… and so I learned not to believe too firmly anything of which I had been persuaded only by example and custom. Thus I gradually freed myself from many errors which may obscure our natural light and make us less capable of heeding reason. But after I had spent some years pursuing these studies in the book of the world and trying to gain some experience, I resolved one day to undertake studies within myself too and to use all the powers of my mind in choosing the paths I should follow… I could do no better than to… devote my whole life to cultivating my reason and advancing as far as I could in the knowledge of the truth.” – René Descartes, ‘Discourse On The Method’
Today we share the thoughts of French philosopher, scientist and mathematician, René Descartes (1596-1650) from a collection of his philosophical writings. Widely considered a seminal figure in the emergence of modern philosophy and science, Descartes is well-known for his ideas on rationalism, mind-body dualism, and the method of doubt. However, it is the famous phrase “Cogito, ergo sum” (“I think, therefore I am”) for which René Descartes is most immediately remembered.
Primary Sources
Quotes are excerpted from ‘The Philosophical Writings Of Descartes’, Volume 1, published by Cambridge University Press in 1994, and ‘The Philosophical Writings Of Descartes’, Volume 2, published by Cambridge University Press in 2008. Both Volume 1 and Volume 2 were translated by John Cottingham, Robert Stoothoff, and Dugald Murdoch.
Quotes From ‘The Philosophical Writings Of Descartes’
Autonomy
“The Lord has made three marvels: something out of nothing; free will; and God in Man.” – Early Writings, ‘Olympian Matters’
“The aim of our studies should be to direct the mind with a view to forming true and sound judgements about whatever comes before it.” – ‘Rules For The Direction Of The Mind’, Rule One
“If… someone seriously wishes to investigate the truth of things, he ought… consider simply how to increase the natural light of his reason…” – ‘Rules For The Direction Of The Mind’, Rule One
“We should attend only to those objects of which our mind seems capable of having certain and indubitable recognition.” – ‘Rules For The Direction Of The Mind’, Rule Two
“All knowledge is certain and evident cognition.” – ‘Rules For The Direction Of The Mind’, Rule Two
“… many people… ingeniously construct the most subtle conjectures and plausible arguments on difficult questions, but after all their efforts they come to realize, too late, that rather than acquiring any knowledge, they have merely increased the number of their doubts.” – ‘Rules For The Direction Of The Mind’, Rule Two
“… the deduction or pure inference of one thing from another can never be performed wrongly by an intellect which is in the least degree rational…” – ‘Rules For The Direction Of The Mind’, Rule Two
“Concerning objects proposed for study, we ought to investigate what we can clearly and evidently intuit or deduce with certainty, and not what other people have thought or what we ourselves conjecture. For knowledge can be attained in no other way.” – ‘Rules For The Direction Of The Mind’, Rule Three
“… let us now review all the actions of the intellect by means of which we are able to arrive at a knowledge of things with no fear of being mistaken. We recognize only two: intuition and deduction… intuition is the indubitable conception of a clear and attentive mind which proceeds solely from the light of reason… deduction in a sense gets its certainty from memory… the first principles themselves are known only through intuition, and the remote conclusions only through deduction.” – ‘Rules For The Direction Of The Mind’, Rule Three
“We need a method if we are to investigate the truth of things.” – ‘Rules For The Direction Of The Mind’, Rule Four
“So blind is the curiosity with which mortals are possessed that they often direct their minds down untrodden paths, in the groundless hope that they will chance upon what they are seeking, rather like someone who is consumed with such a senseless desire to discover treasure that he continually roams the streets to see if he can find any that a passer-by might have dropped.” – ‘Rules For The Direction Of The Mind’, Rule Four
“… it is quite certain that… haphazard studies and obscure reflections blur the natural light and blind our intelligence.” – ‘Rules For The Direction Of The Mind’, Rule Four
“… nothing can be added to the clear light of reason which does not in some way dim it.” – ‘Rules For The Direction Of The Mind’, Rule Four
“… the human mind has within it a sort of spark of the divine, in which the first seeds of useful ways of thinking are sown, seeds which, however neglected and stifled by studies which impede them, often bear fruit of their own accord.” – ‘Rules For The Direction Of The Mind’, Rule Four
“… reason… is a more powerful instrument of knowledge than any other with which human beings are endowed, as it is the source of all the rest.” – ‘Rules For The Direction Of The Mind’, Rule Four
“The whole method consists entirely in the ordering and arranging of the objects on which we must concentrate our mind’s eye if we are to discover some truth. We shall be following this method exactly if we first reduce complicated and obscure propositions step by step to simple ones, and then, starting with the intuition of the simplest ones of all, try to ascend through the same steps to a knowledge of all the rest.” – ‘Rules For The Direction Of The Mind’, Rule Five
“In order to distinguish the simplest things from those that are complicated and to set them out in an orderly manner, we should attend to what is most simple in each series of things in which we have directly deduced some truths from others, and should observe how all the rest are more, or less, or equally removed from the simplest.” – ‘Rules For The Direction Of The Mind’, Rule Six
“… we should not begin our studies by investigating difficult matters.” – ‘Rules For The Direction Of The Mind’, Rule Six
“In order to make our knowledge complete, every single thing relating to our undertaking must be surveyed in a continuous and wholly uninterrupted sweep of thought, and be included in a sufficient and well-ordered enumeration.” – ‘Rules For The Direction Of The Mind’, Rule Seven
“If in the series of things to be examined we come across something which our intellect is unable to intuit sufficiently well, we must stop at that point, and refrain from the superfluous task of examining the remaining items.” – ‘Rules For The Direction Of The Mind’, Rule Eight
“… nothing can be known prior to the intellect…” – ‘Rules For The Direction Of The Mind’, Rule Eight
“Within ourselves we are aware that, while it is the intellect alone that is capable of knowledge, it can be helped or hindered by three other faculties, viz. imagination, sense-perception, and memory.” – ‘Rules For The Direction Of The Mind’, Rule Eight
“We must concentrate our mind’s eye totally upon the most insignificant and easiest of matters, and dwell on them long enough to acquire the habit of intuiting the truth distinctly and clearly.” – ‘Rules For The Direction Of The Mind’, Rule Nine
“In order to acquire discernment we should exercise our intelligence by investigating what others have already discovered, and methodically survey even the most insignificant products of human skill, especially those which display or presuppose order. – ‘Rules For The Direction Of The Mind’, Rule Ten
“… guard against our reason’s taking a holiday while we are investigating the truth about some issue…” – ‘Rules For The Direction Of The Mind’, Rule Ten
“If, after intuiting a number of simple propositions, we deduce something else from them, it is useful to run through them in a continuous and completely uninterrupted train of thought, to reflect on their relations to one another, an to form a distinct and, as far as possible, simultaneous conception of several of them. For in this way our knowledge becomes much more certain, and our mental capacity is enormously increased.” – ‘Rules For The Direction Of The Mind’, Rule Eleven
“Finally we must make use of all the aids which intellect, imagination, sense-perception, and memory afford in order, firstly, to intuit simple propositions distinctly; secondly, to combine correctly the matters under investigation with what we already know, so that they too may be known; and thirdly, to find out what things should be compared with each other so that we make the most thorough use of all our human powers.” – ‘Rules For The Direction Of The Mind’, Rule Twelve
“Where knowledge of things is concerned, only two factors need to be considered: ourselves, the knowing subjects, and the things which are the objects of knowledge. As for ourselves, there are only four faculties which we can use for this purpose, viz. intellect, imagination, sense-perception and memory. It is of course only the intellect that is capable of perceiving the truth, but it has to be assisted by imagination, sense-perception and memory if we are not to omit anything which lies within our power.” – ‘Rules For The Direction Of The Mind’, Rule Twelve
“The intellect can either be stimulated by the imagination or act upon it.” – ‘Rules For The Direction Of The Mind’, Rule Twelve
“… the whole of human knowledge consists uniquely in our achieving a distinct perception of how all these simple natures contribute to the composition of other things.” – ‘Rules For The Direction Of The Mind’, Rule Twelve
“If we perfectly understand a problem we must abstract it from every superfluous conception, reduce it to its simplest terms and, by means of an enumeration, divide it up into the smallest possible parts.” – ‘Rules For The Direction Of The Mind’, Rule Thirteen
“The problem should be re-expressed in terms of the real extension of bodies and should be pictured in our imagination entirely by means of bare figures. Thus it will be perceived much more distinctly by our intellect.” – ‘Rules For The Direction Of The Mind’, Rule Fourteen
“It is generally helpful if we draw these figures and display them before our external senses. In this way it will be easier for us to keep our mind alert.” – ‘Rules For The Direction Of The Mind’, Rule Fifteen
“For things which do not require the immediate attention of the mind, however necessary they may be for the conclusion, it is better to represent them by very concise symbols rather than by complete figures. It will thus be impossible for our memory to go wrong, and our mind will not be distracted by having to retain these while it is taken up with deducing other matters.” – ‘Rules For The Direction Of The Mind’, Rule Sixteen
“We should make a direct survey of the problem to be solved, disregarding the fact that some of its terms are known and others unknown, and intuiting, through a train of sound reasoning, the dependence of one term on another.” – ‘Rules For The Direction Of The Mind’, Rule Seventeen
“For this purpose only four operations are required: addition, subtraction, multiplication and division. The latter two operations should seldom be employed here, for they may lead to needless complication, and they can be carried out more easily later.” – ‘Rules For The Direction Of The Mind’, Rule Eighteen
“… quick… wit,… sharp and distinct… imagination,… ample or prompt… memory… apart from these,… no other qualities… serve to perfect the mind…” – ‘Discourse On The Method’, Part 1
“We have free will, enabling us to withhold our assent in doubtful matters and hence avoid error.” – ‘Principles Of Philosophy’, Part 1- The Principles Of Human Knowledge
“It is not possible for us to doubt that we exist while we are doubting… For it is a contradiction to suppose that what thinks does not, at the very time when it is thinking, exist. Accordingly, this piece of knowledge – I am thinking, therefore I exist – is the first and most certain of all to concur to anyone who philosophizes in an orderly way.” – ‘Principles Of Philosophy’, Part 1- The Principles Of Human Knowledge
“All the modes of thinking that we experience within ourselves can be brought under two general headings: perception, or the operation of the intellect, and volition, or the operation of the will.” – ‘Principles Of Philosophy’, Part 1- The Principles Of Human Knowledge
“Right from infancy our mind was swamped with a thousand… preconceived opinions; and in later childhood, forgetting that they were adopted without sufficient examination, it regarded them as known by the senses or implanted by nature, and accepted them as utterly true and evident.” – ‘Principles Of Philosophy’, Part 1- The Principles Of Human Knowledge
“… our nature consists in thinking…” – ‘Principles Of Philosophy’, Part 1- The Principles Of Human Knowledge
“… nothing has a permanent place, except as determined by our thought.” – ‘Principles Of Philosophy’, Part 2- The Principles Of Material Things
“… there is nothing in us which we must attribute to our soul except our thoughts… the various perceptions or modes of knowledge present in us may be called its passions, in a general sense, for it is often not our soul which makes them such as they are, and the soul always receives them from the things that are represented by them.” – ‘The Passions Of The Soul’, Part 1 – The Passions In General, The Functions Of The Soul
“But the will is by its nature so free that it can never be constrained.” – ‘The Passions Of The Soul’, Part 1 – The Passions In General, 41. The Power Of The Soul With Respect To The Body
“It is by success in… conflicts that each person can recognize the strength or weakness of his soul. For undoubtedly, the strongest souls belong to those in whom the will be nature can most easily conquer the passions and stop the bodily movements which accompany them.” – ‘The Passions Of The Soul’, Part 1 – The Passions In General, 48. How We Recognize The Strength Or Weakness Of Souls, And What Is Wrong With The Weakest Souls
“… passions jostle the will in opposite ways; and since the will obeys first the one and then the other, it is continually opposed to itself, and so it renders the soul enslaved and miserable.” – ‘The Passions Of The Soul’, Part 1 – The Passions In General, 48. How We Recognize The Strength Or Weakness Of Souls, And What Is Wrong With The Weakest Souls
“There is no soul so weak that it cannot, if well-directed, acquire an absolute power over its passions.” – ‘The Passions Of The Soul’, Part 1 – The Passions In General, 50. There Is No Soul So Weak That It Cannot, If Well-Directed, Acquire An Absolute Power Over Its Passions
“But the number of [passions] which are simple and primitive is not very large. Indeed, in reviewing all those I have enumerated, we can easily see that there are only six of this kind – wonder, love, hatred, desire, joy, sadness. All the others are either composed from some of these six or they are species of them.” – ‘The Passions Of The Soul’, Part 2 – The Number And Order Of The Passions, THE ORDER AND ENUMERATION OF THE PASSIONS – 69. There Are Only Six Primitive Passions
“Desire is a passion which has no opposite.” – ‘The Passions Of The Soul’, Part 2 – The Number And Order Of The Passions, THE ORDER AND ENUMERATION OF THE PASSIONS – 87. Desire Is A Passion Which Has No Opposite
“… love, hatred, desire, joy, and sadness… their natural function is to move the soul to consent and contribute to actions which may serve to preserve the body or render it in some way more perfect.” – ‘The Passions Of The Soul’, Part 2 – The Number And Order Of The Passions, THE ORDER AND ENUMERATION OF THE PASSIONS – 137. The Function Of The Five Passions Explained Here, In So Far As They Relate To The Body
“… – thought; this alone is inseparable from me. I am, I exist – that is certain. But for how long? For as long as I am thinking. For it could be that were I totally to cease from thinking, I should totally cease to exist… But what then am I? A thing that thinks.” – ‘Second Meditation’, The Nature Of The Human Mind, And How It Is Better Known Than The Body
“… all that the intellect does is to enable me to perceive the ideas which are subjects for possible judgements…” – ‘Fourth Meditation’, Truth And Falsity
“… I cannot complain that the will or freedom of choice which I received from God is not sufficiently extensive or perfect, since I know by experience that it is not restricted in any way. Indeed, I think it is very noteworthy that there is nothing else in me which is so perfect and so great…” – ‘Fourth Meditation’, Truth And Falsity
Social Capital
“Every man is indeed bound to do what he can to procure the good of others, and a man who is of no use to anyone else is strictly worthless.” – ‘Discourse On The Method’, Part 6
“The power which men have over each other was given them so that they might employ it in discouraging others from evil…” – ‘Principles Of Philosophy’, Part 1- The Principles Of Human Knowledge
Trust
“… it is prudent never to trust completely those who have deceived us even once.” – ‘First Meditation’, What Can Be Called Into Doubt
Virtues
“… hardly anyone gives a thought to good sense – to universal wisdom… what makes us stray from the correct way of seeking the truth is chiefly our ignoring the general end of universal wisdom.” – ‘Rules For The Direction Of The Mind’, Rule One
“… our faith has a basis in our intellect.” – ‘Rules For The Direction Of The Mind’, Rule Three
“Good sense is the best distributed thing in the world: for everyone thinks himself so well endowed with it that even those who are the hardest to please in everything else do not usually desire more of it than they possess.” – ‘Discourse On The Method’, Part 1
“The greatest souls are capable of the greatest vices as well as the greatest virtues…” – ‘Discourse On The Method’, Part 1
“… there is none that leads weak minds further from the straight path of virtue than that of imagining that the souls of the beasts are of the same nature as ours, and hence that after this present life we have nothing to fear or to hope for, and more than flies and ants.” – ‘Discourse On The Method’, Part 5
“… the word ‘philosophy’ means the study of wisdom, and by ‘wisdom’ is meant not only prudence in our everyday affairs but also a perfect knowledge of all things that mankind is capable of knowing, both for the conduct of life and for the preservation of health and the discovery of all manner of skills… men can be said to possess more or less wisdom depending on how much knowledge they possess of the most important truths.” – ‘Principles Of Philosophy’, Preface to the French edition published 1647
“… human beings, whose most important part is the mind, should devote their main efforts to the search for wisdom, which is the true food of the mind.” – ‘Principles Of Philosophy’, Preface to the French edition published 1647
“Now just as it is not the roots or the trunk of a tree from which one gathers the fruit, but only the ends of the branches, so the principal benefit of philosophy depends on those parts of it which can only be learnt last of all.” – ‘Principles Of Philosophy’, preface to the French edition published 1647
“… no one acquires a great reputation for piety more easily than the superstitious or hypocritical person.” – ‘Dedicatory Letter To Elizabeth’
“… the pure and genuine virtues, which proceed solely from knowledge of what is right, all have one and the same nature and are included under the single term ‘wisdom’. For whoever possesses the firm and powerful resolve always to use his reasoning powers correctly, as far as he can, and to carry out whatever he knows to be best, is truly wise, so far as his nature permits. And simply because of this, he will possess justice, courage, temperance, and all the other virtues; but they will be interlinked in such a way that no one virtue stands out among the others… Now there are two prerequisites for the kind of wisdom just described, namely the perception of the intellect and the disposition of the will.” – ‘Dedicatory Letter To Elizabeth’
“There is no more fruitful exercise than attempting to know ourselves.” – ‘Description Of The Human Body And Of All Its Functions’, Part 1 – Preface
“The function of all the passions consists solely in this, that they dispose our soul to want the things which nature deems useful to us, and to persist in this volition…” – ‘The Passions Of The Soul’, Part 2 – The Number And Order Of The Passions, 52. The Function Of The Passions, And How They May Be Enumerated
“Wonder is joined to either esteem or contempt, depending on whether we wonder at the value of an object or at its insignificance. Thus we may have esteem or contempt for ourselves; this gives rise to the passions of magnanimity or vanity and humility or abjectness, and then to the corresponding habits… But when our esteem or contempt is directed upon some other object that we regard as a free cause capable of doing good and evil, esteem becomes veneration and simple contempt becomes scorn… All the preceding passions may be produced in us without our perceiving in any way whether the object causing them is good or evil. But when we think of something as good with regard to us, i.e. as beneficial to us, this makes us have love for it; and when we think of it as evil or harmful, this arouses hatred in us… This same consideration of good and evil is the origin of all the other passions… We are prompted to desire the acquisition of a good or the avoidance of an evil simply if we think it possible to acquire the good or avoid the evil. But when we go beyond this and consider whether there is much or little prospect of our getting what we desire, then whatever points to the former excites hope in us, and whatever points to the latter excites anxiety (of which jealousy is one variety). When hope is extreme, it changes its nature and is called ‘confidence’ or ‘assurance’ just as, on the other hand, extreme anxiety becomes despair.” – ‘The Passions Of The Soul’, Part 2 – The Number And Order Of The Passions, THE ORDER AND ENUMERATION OF THE PASSIONS – 54. Esteem And Contempt, Generosity Or Pride, And Humility Or Abjectness; 55. Veneration And Scorn; 56. Love And Hatred; 57. Desire; 58. Hope, Anxiety, Jealousy, Confidence And Despair
“Generosity prevents us from having contempt for others… the most generous people are usually also the most humble. We have humility as a virtue when, as a result of reflecting on the infirmity of our nature and on the wrongs we may previously have done, or are capable of doing (wrongs which are no less serious than those which others may do), we do not prefer ourselves to anyone else and we think that since others have free will just as much as we do, they may use it just as well as we use ours… Those who are generous in this way are naturally led to do great deeds, and at the same time not to undertake anything of which they do not feel themselves capable. And because they esteem nothing more highly than doing good to others and disregarding their own self-interest, they are always perfectly courteous, gracious and obliging to everyone. Moreover they have complete command over their passions. In particular, they have mastery over their desires, and over jealousy and envy, because everything they think sufficiently valuable to be worth pursuing is such that its acquisition depends solely on themselves; over hatred of other people, because they have esteem for everyone; over fear, because of the self-assurance which confidence in their own virtue gives them; and finally over anger, because they have very little esteem for everything that depend on others, and so they never give their enemies any advantage by acknowledging that they are injured by them.” – ‘The Passions Of The Soul’, Part 3 – Specific Passions – 154. Generosity Prevents Us From Having Contempt For Others; 155. What Humility As A Virtue Consists In; 156. The Properties Of Generosity; And How Generosity Serves As A Remedy Against All The Disorders Of The Passions
“It should be noted that what we commonly call ‘virtues’ are habits in the soul which dispose it to have certain thoughts…” – ‘The Passions Of The Soul’, Part 3 – Specific Passions – 161. How Generosity May Be Acquired
“… if we occupy ourselves frequently in considering the nature of free will and the many advantages which proceed from a firm resolution to make good use of it – while also considering, on the other hand, the many vain and useless cares which trouble ambitious people – we may arouse the passion of generosity in ourselves and then acquire the virtue. Since this virtue is, as it were, the key to all the other virtues and a general remedy for every disorder of the passions, it seems to me that this consideration deserves serious attention.” – ‘The Passions Of The Soul’, Part 3 – Specific Passions – 161. How Generosity May Be Acquired
“… the chief use of wisdom lies in its teaching us to be masters of our passions and to control them with such skill that the evils which they cause are quite bearable, and even become a source of joy.” – ‘The Passions Of The Soul’, Part 3 – Specific Passions – 212. It Is On The Passions Alone That All The Good And Evil Of This Life Depends
“For us who are believers it is enough to accept on faith that the human soul does not die with the body, and that God exists; but in the case of unbelievers, it seems that there is no religion, and practically no moral virtue, that they can be persuaded to adopt until these two truths are proved to them by natural reason. And since in this life the rewards offered to vice are often greater than the rewards of virtue, few people would prefer what is right to what is expedient if they did not fear God or have the expectation of an after-life.” – ‘Dedicatory Letter To The Sorbonne’
Final Thoughts
René Descartes’ philosophical legacy extends far beyond his famous declaration “I think, therefore I am.” Through this collection of his writings, we witness a thinker deeply committed to the cultivation of reason and the systematic pursuit of truth. His emphasis on methodical doubt, clear and distinct perception, and the primacy of intellectual intuition established a framework that would shape Western philosophy for centuries to come. Yet what emerges most powerfully from these passages is not merely an abstract system of thought, but a practical philosophy aimed at human flourishing—one that seeks to harmonize our rational capacities with our emotional lives, and to ground ethical action in genuine understanding rather than custom or authority.
The interconnection between Descartes’ epistemology and his ethics reveals itself throughout these excerpts. His insistence that we must “direct the mind with a view to forming true and sound judgements” is not merely an intellectual exercise but a moral imperative. For Descartes, the cultivation of wisdom through proper method leads naturally to virtue, as those who possess “the firm and powerful resolve always to use his reasoning powers correctly” will inevitably develop justice, courage, and temperance. This unity of knowledge and virtue finds its highest expression in the concept of generosity—that magnanimous disposition that combines proper self-esteem with genuine regard for others, serving as “the key to all the other virtues and a general remedy for every disorder of the passions.”
In our current age of information overload and competing truth claims, Descartes’ methodical approach to knowledge acquisition remains remarkably relevant. His warning against “haphazard studies and obscure reflections” that “blur the natural light and blind our intelligence” speaks directly to our need for intellectual discipline in navigating complex modern challenges. Moreover, his vision of philosophy as ultimately practical—aimed at mastering our passions, conducting our lives wisely, and contributing to the good of others—reminds us that the pursuit of truth is not an isolated academic exercise but a fundamental human responsibility. As we face unprecedented ethical dilemmas in technology, medicine, and social organization, Descartes’ faith in reason’s ability to guide us toward genuine human flourishing offers both inspiration and a demanding standard by which to measure our own philosophical efforts.
Thanks for reading!