René Descartes’s Theory of Knowledge and The Discourse on the Method: Summary and Key Concepts

René Descartes’s theory of knowledge was first articulated in his famous work The Discourse on the Method, but was fully developed in his later famous work Meditations on First Philosophy.

Descartes was considered the Father of Modern Philosophy. He was also the first major figure in the philosophical movement in the modern period known as rationalism. Rationalism can be viewed from two vantage points, namely, as a method and as a doctrine.

On the one hand, rationalism can be viewed as a method of understanding the world based on the use of reason as the means to attain knowledge. On the other hand, rationalism can be viewed as a doctrine in epistemology which regards reason as the chief source and test knowledge. 

Key Concepts in Descartes’s Theory of Knowledge

One of the key concepts that we need to remember in Descartes’ theory of knowledge is the idea that sense perception is unreliable. As a matter of fact, Descartes rejects the idea that sense perception conveys accurate information. Thus, it could be said that one of the goals of Descartes is to distinguish what is true from what is false. In doing so, Descartes employs the famous methodic doubt where he doubts everything believed to be true until certainty is attained. In this process, ideas are put in rigorous test in determining its certainty. As is well known, the methodic doubt is the central concept of Descartes’ first published work titled The Discourse on the Method.

The second key concept in Descartes’ theory of knowledge is the idea that reason is the essence of humanity. For Descartes, the very act of thinking offers a proof of individual human existence. Hence, thought and reason, according to Descartes, must be the essence of humanity. In fact, as Descartes argues, a human person would still be human even without hands or hair as long as he has reason, that is, the ability to think creatively. And because only humans have the ability to think, animals, therefore, don’t think. According to Descartes, animals act based on their instinct.

The third key concept that we need to remember in Descartes’ theory of knowledge is the claim that knowledge can attained. As we can see, Descartes emphasized this point as a response to the claims of the skeptics that we cannot attain knowledge. For Descartes, reason is a native gift. And Descartes believes that true knowledge can be attained though the methodical application of reason.

Descartes’ Discourse on the Method

The Discourse on the Method is Descartes’ first published work. It was written in Latin, rather than in French. It must be noted that during the time of Descartes, Latin was still the accepted language of scholarship. Hence, the attempt to write in language other than Latin during this time was revolutionary.

The Discourse on the Method is also Descartes’ attempt to explain his method of reasoning, which contains six (6) parts. In what follows, I will briefly sketch the key concepts of each part.

Part I: On Good Sense

One of the main points of Part I of Descartes’ Discourse on the Method is idea that people possess “good sense”. Descartes understands good sense as the ability to distinguish truth from fiction.

According to Descartes, because people possess good sense, it is therefore not the lack of ability to think that obstructs people from attaining truth, but their failure to follow the correct path of reasoning. Thus, as Descartes argues, it is the use of a method that can elevate an average mind above the rest. In fact, Descartes considers himself as an average thinker improved by the use of his method.

Part II: On Methodic Doubt

It is in Part II of the Discourse on the Method that Descartes lays down the rules which he believes is the way to certainty. As is well known, this method was famously known as the “methodic doubt”. This method involves four (4) steps, namely:

1. To never believe in anything unless she can prove it herself.

2. To reduce every problem to its simplest parts.

3. To always be orderly in one’s thoughts and proceed from the simplest part to the most difficult.

4. To always, when solving a problem, create a long chain of reasoning and leave nothing out.

Part III: Descartes’ Moral Code

It is in Part III that Descartes puts forth a provisional moral code to live by, namely:

1. To obey the rules and customs of one’s country and religion and never take on extreme opinion.

2. To be decisive and stick with one’s decisions, even if some doubts linger.

3. To try to change one’s self, and not the world.

4. To examine all professions in the world and try to figure out what the best one is.

Part IV: Descartes’ Arguments for God’s Existence

In Part IV of the Discourse on the Method, Descartes offers his argument for God’s existence. Contemplating the nature of dreams and the unreliability of the sense, Descartes becomes aware of his own processes of thinking. Descartes eventually realizes that “thinking” is a proof of his existence.

Now, because Descartes has the ability to doubt, he believes that he is imperfect. But because someone has the ability to conceive of perfection, then, for Descartes, it follows that something or someone perfect must exist outside of him, namely, God. Therefore, God exists. And for Descartes, all things in the world, including clear and distinct ideas, comes from God.

Part V: On the Immortality of the Soul

One of the highlights of Part V is Descartes’ discussion on the immortality of the soul.

Descartes believes that the soul has a life outside of the body. Thus, for Descartes, the soul could not perish. The soul, therefore, is immortal. Descartes, however, did not provide any proofs as to the existence of the soul outside the body.

It must be noted, however, that Descartes equates the soul with mind.  Hence, the soul for Descartes can be understood as reason, that is, the rational soul.

Part VI: On Physics

Part VI is the concluding part of the Discourse on the Method. It touches on the possible conflict between the Church and Descartes’ view on physical science.

It must be noted that Descartes supports Galileo’s heliocentrism, and because Galileo was excommunicated by the Church, Descartes was very careful in the end so as not to experience Galileo’s fate.

It is also in Part VI that Descartes shows the practical application of his method in mathematics and the physical sciences.