Descartes was a French philosopher, mathematician and scientist born in 1596 in La Haye, France. He is best known for his philosophical text Meditations on First Philosophy where he seeks to doubt everything he has ever learned, in order to see what it is that he can actually know with certainty. Descartes soon realizes that the only thing he is certain of is that, since he is doubting, he must be thinking. This leads him to famously remark “I think, therefore I am” (cogito ergo sum). From this fundamental principle, he puts forth what he believes are rational arguments for the existence of God as well as the world. Descartes is considered to be the “Father of Modern Philosophy” and was a key figure of the Scientific Revolution in the 17th century.
While Descartes had grown up with a liberal education, he ultimately came to question whether what he had learned in school was actually true. He noticed that in philosophy, any position that one philosopher gave, another would argue the exact opposite. Descartes was therefore attracted to mathematics, because of the certainty upon which the truths of Euclidean geometry were based. As had been popular at the time, Descartes travelled throughout Europe, and on his journey he came to the realization that it would be possible to ground all knowledge in the same certainty as mathematics. He would then move to the Netherlands, in order to get away from the distractions and social life in France, in order to write his philosophy.
In addition to being a philosopher, Descartes was also a famous mathematician and scientist. In his Discourse on Method, he explains that the way for progress to be made in searching for truth and knowledge is to start with what is known, and to logically and rationally proceed from there to draw out the necessary conclusions. Descartes is considered a rationalist, because he sees knowledge as rooted in reason. Scientific experiments are valuable because they allow us to gather data about the outside world, which then through reason we can use to increase our understanding. In the Discourse, he would also put forth a request to the scientific community of Europe that everyone work together in order to benefit from everyone’s research and experiments. As such, he would envision the way science is practiced today.
In Descartes most famous work, Meditations on First Philosophy, Descartes seeks to doubt everything (what is known as “methodological skepticism”), in order to see what truly can be known with certainty. Descartes realizes that the only thing he can truly know is that he exists. Since he is doubting, he must be a thinking thing. He therefore proclaims, “I think therefore I am” (in latin: cogito ergo sum). The fact that he exists as a thinking thing is so clear to him, that he believes he has found the fundamental principle upon which he can ground all that can be said to be true.
Although Descartes was himself a scientist, he recognized that the senses can be deceptive. He famously uses the example of wax. He explains that in one state a piece of wax can have a certain color and shape, however when heated, it takes on a completely different shape and color. Everything about the wax, all of its sensible properties, are changed. From this, Descartes reasoned that the senses can only tell us about the appearance of things, but not about their true nature. Descartes believed that true knowledge must therefore be based not on sensory experience, but on reason. This is known as rationalism.
In the Meditations, Descartes then realizes that it is possible that there are no external things in the first place. The world could be an illusion, since he could either be dreaming, or alternatively he could be deceived by what he calls an “evil genius.” Descartes will only be able to overcome this skeptical doubt by explaining that, since God is perfect, God would not deceive him in this way.
In order to do this, Descartes must prove that God exists. In the Meditations, he gives two arguments for the existence of God. First, Descartes puts forth what is known as the Ontological Argument which states that God must exist because of his very nature. Descartes explains that just as a triangle must necessarily have three sides due to its nature, likewise since God is perfect, he must therefore necessarily exist. This is because certainly something that exists is more perfect than something that doesn’t exist. This argument was originally put forth by the 11th century Christian philosopher Anselm of Canterbury.
Second, Descartes argues that God must exist based on his belief that any idea must have been caused by something with an equal or greater degree of reality. Descartes explains, therefore, that since he had the idea of God as an infinite being, the only thing with enough reality to cause this idea would therefore be this infinite being itself. Therefore, Descartes believes he has found a second rational argument for God’s existence. These arguments have been highly criticized, since for example, one can have an idea of a perfect island without that island actually existing.
By “proving” God’s existence as a perfect being, Descartes was therefore able to assure himself that he was neither sleeping nor being deceived by an evil demon, and therefore able to be confident that the world did in fact exist. The logic which Descartes uses in the Meditations here is referred to as the “Cartesian Circle,” since it seems that he is proving something on the basis of that which he is trying to prove. Descartes believes knowledge can only come from seeing that something is “clearly and distinctly” true. He sees God existing as clearly and distinctly being true. However, his whole basis for believing anything is that God exists and as a perfect being wouldn’t deceive him. Therefore, he is only able to be certain that God exists because of the certainty that God gives him, and in this way argues “in a circle.”
Descartes explains that, while he personally believes in God on the basis of faith, the reason he is offering these rational proofs for God’s existence in the first place is to try and convince nonbelievers (skeptics and atheists) who wouldn’t accept Christianity otherwise. Descartes believed it was important for people to follow religion, since without a belief in an afterlife, people were more likely to commit bad deeds. He believed his philosophy was therefore able to strengthen Christian theology, although the Meditations ultimately was banned by the Catholic Church. In his time, the Christian philosopher Pascal would criticized Descartes for attempting to rationalize a religion which was rooted in faith in God and “the mysteries.”
Descartes will debate with others about scientific, mathematical, and philosophical issues throughout his lifetime. He actually requested for the intellectuals living in Paris at the time, such as the philosopher Thomas Hobbes, to respond to his Meditations, so that he could respond to their objections. While the French philosopher and scientist Pascal seemed to have proven that vacuums exist in nature, based on his experiments with barometers, Descartes believed that the concept of a vacuum was impossible. He believed that all matter was extended in space, and therefore a vacuum, a matter with no extension, was a logical contradiction. Likewise, Descartes argued against those who believed that the world was fundamentally composed of atoms, instead arguing that things were infinitely divisible.
Descartes is famous for contrasting matter with soul, or that which is immaterial. This is known as Cartesian dualism. Descartes recognized that as human beings, our thoughts cause our bodies to do things, and likewise our bodies can cause thoughts to occur in our minds. The understanding of ourselves as human beings that are composed of a body and a mind has deeply influenced Western thought since as science continues to try and better understand this relationship. Descartes believed that what separates humans from animals is that animals don’t have minds. He believed that animals therefore do not experience pain, but are simply mechanical beings that elicit a response. This belief allowed him to comfortably perform vivisections (i.e. the dissection of animals while they are still alive).
Descartes is considered to be the “Father of Modern Philosophy” because he represents a break with the philosophical and scientific tradition of the past that was rooted in the thoughts of Aristotle. First, along with others such as Galileo, Descartes sought to demonstrate that the sun, and not the Earth as Aristotle had believed, was the center of the universe. Second, before Descartes most scientists and philosophers embraced Aristotle’s understanding of the world as being made up of particular substances that have a certain form which determines their character. Aristotle believed that a stone, for example, by its nature seeks to fall to the ground. Because of Descartes sharp distinction between material and immaterial things, he saw this sort of thinking as improperly attributing intentions to material objects. Likewise, he rejected Aristotle’s belief in final causes, that the things of the world are directed towards certain ends (this is known as teleology). For Descartes, the world was to be understood in purely mechanical terms, as Newton would later describe.
Descartes appeals to us in modern times because of his emphasis on mathematics, science, and the use of reason. His philosophical arguments are a good test of one’s ability to follow a logical argument, and to determine for oneself whether it is really rational or not. Descartes’ skeptical idea that we may be dreaming comes from the earlier French philosopher Montaigne, meanwhile his idea that we may be deceived by an evil demon in recent times has been reimagined in the scenario that our brains are being artificially stimulated while being preserved in a jar (known as the “brain in a vat” scenario). The tradition of seeing knowledge as coming from reason, known as Rationalism, would be continued by the philosophers and mathematicians Spinoza and Leibniz. In contrast, the belief that knowledge comes primarily through the senses, known as Empiricism, would arise in the philosophies of Locke, Berkeley, and Hume. In this way, Descartes set the trajectory for Modern philosophy which would culminate with Kant in the 18th century.