Understanding 5 Famous Quotes by Descartes

Descartes teaches us to actively engage our minds, question assumptions, and seek clarity in our pursuit of knowledge.

May 6, 2024By Viktoriya Sus, MA Philosophy

quotes rene descartes explained


Considered one of the most significant European figures in science and culture during the seventeenth century, the French philosopher, mathematician, and physicist René Descartes was also responsible for creating modern algebraic symbolism as well as analytical geometry.


Additionally, he conceived radical doubt as a philosophical method and viewed physics through a mechanistic lens. His notions regarding rationalistic knowledge of the world were integral to the history of philosophy; they are found throughout his Discourse on the Method.


What are some of his most enduring quotes that capture his philosophy?


1. “Cogito, Ergo Sum” (I Think, Therefore I Am)

patti mayor woman thinking painting
Woman Thinking, Patti Mayor, 19th century, via ART.UK


Descartes’ famous phrase, “Cogito, ergo sum,” or “I think, therefore I am,” is at the heart of his philosophy. It was intended to provide Descartes with a starting point for establishing certain knowledge.

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Doubt plays an important role in Descartes’ philosophy. He wanted to find a secure foundation for knowledge. He takes us on his philosophical journey in Discourse on Method and Meditations. By doubting everything—including his own existence and the existence of the external world—Descartes realizes that he cannot doubt his own doubting. The very act of doubting requires some thinking entity, which he identifies as “I.”


In saying, “I think, therefore I am,” Descartes argued that thinking and existing are one and the same thing. If someone is questioning or doubting their own existence, then they must exist—even if it is just as someone doing the questioning or experiencing the doubt.


The method of radical doubt and the conclusion that “the thinking self” exists have far-reaching implications: they affirm the primacy of mind (or consciousness) and rationality in understanding reality.


To illustrate, imagine someone sitting alone in a room pondering whether anything they see or experience is real or just an illusion. However, as they are still engaged with these thoughts, their actions show that they exist as thinking beings—regardless of whether what’s outside their mind is real or illusory, even if it is all an illusion created by some evil demon.


Descartes’ phrase raises issues about who we are as human beings and how our minds relate to our bodies. It implies that perhaps our minds or consciousness can be separated from our physical bodies. This philosophical position is called Cartesian dualism.


2. “Divide Each Difficulty into as Many Parts as Is Feasible and Necessary to Resolve It”

nigel henderson shattered glass painting
Untitled No. 8 (Shattered Glass), Nigel Henderson, 1959, via TATE


Descartes propounds a pragmatic and methodical approach to problem-solving. If complex problems are broken down into simpler, more understandable parts, he suggests, then clarity and solutions can be reached. This would lend us an organized manner of dissecting the difficulties involved, writes Descartes. It would prevent us from getting confused by it all and also help us get a better grip on the many parts that make up the larger difficulty. Herein lies Descartes’ philosophical emphasis on rationality and logical thinking.


Suppose you aim to design a better smartphone. Break your task down into its components: you have hardware, software, user experience, and market competition. You may begin with the hardware requirement: what processing power will your device require? What about battery life or camera quality? Moving on, think of its software: what is going to be your operating system? Will there be third-party apps? Now consider user experience: how ergonomic is its design? How intuitive will its interface be? Finally, assess market competition: which rival products exist in the marketplace? What do consumers want from such a device?


Thinking about it this way helps you address each constituent part and improve your understanding of the challenges and opportunities presented, rather than being overwhelmed by complexity at day one. As captured in this first quote, Descartes advises us to break down our problems so we can look at them both completely and systematically. When taken apart, they become easier to understand and solve. It also suggests that our endeavors should be guided by reason and not instinct as we aim at clarity. These two recommendations still make about as much sense today as they did when Descartes set his pen aside nearly 400 years ago.


3. “The Reading of All Good Books Is Like a Conversation with the Finest Minds of Past Centuries”

jean honoré fragonard young girl painting
Young Girl Reading, Jean Honoré Fragonard, 1769, via National Gallery of Art


Descartes was a great believer in the power of knowledge. The famous philosopher thought that we should read as many good books as possible. Why? Because Descartes believed that reading good books is like having a conversation with the greatest minds of the past. And if you want to be smart and knowledgeable, he said, you need to have conversations with them.


What are “good books?” Descartes did not say exactly. But here is what we think he meant: They’re ones that make profound arguments and were written by some of the most brilliant people who ever lived. That is because when you read those sorts of books, you expose yourself to many different ways of thinking. You see things through other people’s eyes and learn how they think.


Doing this can help us develop our critical thinking skills and challenge our own beliefs—even if it is just while we are sitting on a train or bus reading a book.


We can do this when we pick up one of his works, such as Meditations on First Philosophy. When Descartes wrote this philosophical treatise in 1641-42, one aim was for readers to engage directly with him—at least intellectually speaking—by reflecting on his arguments about doubt. By doing so, they would hopefully start questioning their own assumptions more often and be open to new ideas. Reading certain works by other influential individuals also allows us to have similar conversations with some really clever people who have been dead for centuries.


Take Plato’s The Republic (c380 BCE). By engaging with it through its dialogues between Socrates and others, readers get an opportunity not only to converse intellectually but also explore ideas around justice or consider what an ideal society would look like. Or, readers may ask themselves why humans behave the way they do.


4. “It Is Not Enough to Have a Good Mind; the Main Thing Is to Use It Well”

jan matejko wise fool painting
Wise Fool (Stańczyk), Jan Matejko, 1862, via Wikimedia Commons


Renowned as the father of modern philosophy, Descartes espoused reason as the bedrock of knowledge. He contended that an individual could employ their reason to arrive at certainties by means of his celebrated method of doubt. This technique entails systematically doubting all beliefs and opinions until arriving at things one cannot doubt. The aim is to establish secure foundations for knowledge that are independent of sensory perception or imagination.


In this quote, Descartes urges individuals not just to possess intelligence but also to put their minds in gear through critical thinking and reasoning. The phrase “having a good mind” suggests having intellectual abilities, understanding, and knowledge. But in Descartes’ view, these are only valuable if properly used.


Imagine someone with a brilliant mind who can grasp complex ideas. This person may have potential intelligence beyond measure. But if they do not use it—if they do not tackle problems or contribute meaningfully in discussions—their intelligence remains untapped.


By contrast, another person might be less naturally gifted but consistently exerts themself on using whatever mental apparatus they possess well. By putting more effort into using their mind well, this person might achieve more intellectually and make greater contributions to society than the first person ever does with all their potential gifts.


Descartes’ philosophy stresses the active use of reason and critical thinking: true worth lies in application rather than mere possession. Merely, “having a good mind” is not enough; you must also harness it through reasoning critically. Such employment is key because, without it, we would not gain knowledge, solve problems, or make advances that benefit the wider society.


5. “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”

What is Truth. Christ and Pilate, Nikolai Ge, 1890, via WikiArt


This quote from Descartes again conveys the importance of doubt in the search for truth. It stressed that one should embrace doubt if they unerringly wish to uncover what is true about their lives.


Central to Descartes’ philosophy was skepticism: the view that our knowledge and beliefs are uncertain and, therefore, open to doubt. He famously introduced “methodical doubt,” where he questioned everything he believed or knew previously and sought a secure foundation for truth. By stripping away all assumptions and preconceptions, Descartes believed individuals could arrive at indubitable truths; ones beyond any possibility of doubt.


Descartes illustrated his point with an example: his famous thought experiment known as The Evil Demon Hypothesis (sometimes referred to as The Malicious Demon). This involved entertaining the idea that there could be an all-powerful being who is systematically deceiving us about everything we believe or take for granted— even basic perceptions about the world around us. By jolting people out of complacency and encouraging them to question how certain they can really be about anything at all, it opens up space for critical thinking and self-examination.


Engaging in this sort of systematic doubting allows us to pick through our ideas, theories, and beliefs, separating the wheat from the chaff; finding what is true among what is false, and identifying what is certain amid uncertainty. Doubt serves progress by opening minds up to fresh possibilities—new perspectives on old problems or questions.


For instance, imagine someone raised in a deeply religious family who starts questioning their inherited beliefs. By subjecting those convictions to methodical doubt, they might interrogate those beliefs critically: are they warranted? How do my views measure up against alternative interpretations or evidence? This kind of process advocated by Descartes might lead them eventually to a greater understanding of what they believe or a new way of thinking altogether.


In short, Descartes’ quote is about intellectual honesty. It is about having the courage to interrogate the beliefs we hold dearly if we genuinely seek truth. By doubting—that is, by subjecting assumptions, knowledge, and belief to rigorous analysis and scrutiny—individuals can arrive at a more genuine and enlightened understanding of the world.


So, What Does Descartes Teach Us?

jan baptist weenix rene descartes painting
Portrait of René Descartes, Jan Baptist Weenix, c. 1647-49, via Wikimedia Commons


In our quest for knowledge and truth, Descartes shows us the importance of critical thinking and rationality. He wants us to doubt things—this is a tool that opens up space in which we can genuinely inquire. Methodical doubt also tells us that we need a solid foundation for our knowledge, free from the vagaries of sense perception or imagination.


Further, engaging with great thinkers from the past can transform you intellectually. Read them; talk to them as though they were still alive, he says: it is worth trying to get at their wisdom because it expands your horizons. This suggests that intellectual growth is not all about what you were born with; it is about what you do with your mind.


Nor is just having a good mind enough: we must use it well, too, through careful analysis, reasoning, and critical thinking. It underlines the idea that you do not just acquire knowledge by passively taking in the world. Instead, acquiring knowledge means actively engaging with material through disciplined thought.


So basically, we find three key lessons captured in these quotes explored here: the virtue of doubt, the importance of talking to good-thinking deceased individuals, and what comfort there might be in knowing that really using your brain is its own reward.

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By Viktoriya SusMA PhilosophyViktoriya is a writer from L’viv, Ukraine. She has knowledge about the main thinkers. In her free time, she loves to read books on philosophy and analyze whether ancient philosophical thought is relevant today. Besides writing, she loves traveling, learning new languages, and visiting museums.