after Frans Hals [Public domain], via Wikimedia Commons
René Descartes (1596-1650) lived in an age of skepticism. The New Science had grown to be very important, and it had brought into question many of the beliefs that had been held by the Church. For example, the Church had believed that the Earth is at the center of the universe, and that the Sun orbits around the Earth. However, the Polish astronomer Copernicus (1473-1543) became famous for his heliocentric theory that stated that the Sun is at the center of the solar system and that the Earth orbits around the Sun. Other scientists such as the Italian astronomer Galileo (1564-1642) believed in the Copernican theory. Many people were unsure what to believe: what the Church told them, or what the scientists told them.
Descartes was also aware that philosophy finds it difficult to come up with definitive answers to its perennial questions. (Of course, if a definitive answer could be found to a philosophical question, the issue would no longer be philosophical, and philosophers would move on to other questions.) Despite his excellent education by the Jesuits (who are known for providing excellent educations), Descartes found himself wracked by doubt.
Because of his aversion to skepticism (the position that knowledge is impossible to acquire), Descartes made it his life’s work to put philosophy on a firm foundation. In fact, Descartes wanted to find something that is impossible to doubt — that is, something that cannot be doubted — to serve as the basis for his philosophy.
To conquer his doubt, Descartes decided to use methodic doubt. He would doubt everything that could possibly be doubted until he discovered something that could not be doubted. This would be the firm foundation for philosophy for which he was searching.
Doubting the Senses
To begin his methodic doubt, Descartes focused on his senses: seeing, hearing, touching, smelling, and tasting. He discovered that his senses were unreliable. For one thing, we are fooled by optical illusions. Square towers, when seen from a distance, look round. Large people, when seen from a distance, look small. In addition, Descartes points out, he has often dreamed that he was awake. While dreaming, he thought he was awake, and it was not until he woke up that he discovered his error. So even while writing the lines people still read hundreds of years after they were written, Descartes believed that he could doubt that he was awake.
Next in his methodic doubt, Descartes doubts such truths as that 2 + 3 = 5, and that squares have four sides. You may object: Surely these things are true whether I am sleeping or not. Perhaps not, Descartes replies, because for all I know, there may be a deceiving demon who makes me think up is down, and square is round. So perhaps 2 + 3 really equals 6, and perhaps a square is really a circle. The deceiving demon may be making me think false things are true. (This device of the deceiving demon shows just how seriously Descartes took his methodic doubt; he really did want to discover something that it was impossible to doubt.)
Cogito Ergo Sum
Having doubted all these things, Descartes now discovers something that it is impossible to doubt. And that is that he is doubting — as well as thinking, affirming, denying, wishing, and other intellectual activities. And if he is doubting, he must exist in order to be doubting. Therefore, Descartes writes: Cogito ergo sum. This is Latin for “I think, therefore I am.” This is the thing that cannot be doubted, even if there is a deceiving demon around. After all, if the deceiving demon deceives me, I must exist in order to be deceived. As Descartes writes, “I am, I exist — that is certain….”
What Kind of Thing am I?
So Descartes knows that he exists, but he then asks what kind of thing is he. His answer is that he is a thinking thing. Descartes performs a large number of intellectual activities: He doubts, he thinks, he wishes, he understands, he conceives, etc. Because of these things, Descartes says that he is a thinking thing.
In his other Meditations, Descartes goes on to show that he also has a body (and that God and physical objects exist). Descartes is a Dualist: He believes that he consists of two things:
1) an immaterial mind, which thinks and which is not extended in space, and
2) a material body, which is extended in space.
Since Descartes first established the existence of the mind, then the existence of the body, he felt that human beings consist of two different things.
The Wax Example
In addition to being a Dualist, Descartes was a Rationalist. As such, he believed that knowledge is acquired from the use of our reason, not our senses. As we have already seen, our senses frequently deceive us. To show that we acquire knowledge by the use of our reason, Descartes asks us to think about a piece of beeswax.
So imagine that you have a piece of beeswax fresh from a hive. What do your senses tell you about the beeswax?
- You can taste the honey that was stored in the beeswax.
- You can smell the flowers visited by the bees that made the beeswax and the honey.
- You can see the color, shape, and size of the beeswax.
- You can feel the coldness and the hardness of the beeswax.
- You can hear a sound if you rap on the beeswax.
In short, all your senses tell you that this is a piece of beeswax freshly taken from the hive.
But next imagine that you put the piece of beeswax close to a fire so that the fire heats the beeswax. What do your senses then tell you about the piece of beeswax?
- The taste of the honey has vanished.
- The odor of flowers has vanished.
- The beeswax changes color.
- The beeswax loses its shape.
- The beeswax increases in size.
- The beeswax becomes liquid.
- The beeswax grows hot.
- If you rap on the beeswax, it gives out no sound.
In short, the sensory information received from the piece of beeswax brought close to a fire is completely different from the sensory information received from the piece of beeswax before it was brought close to a fire.
If we were to gain knowledge only from our senses, we would have to conclude that the cold beeswax and the hot beeswax were two completely different substances, because this is what our senses tell us. But of course, we realize that the cold beeswax and the hot beeswax are both the same substance: beeswax. Therefore, Descartes says, it is our reason — not our senses — that tells us that the cold beeswax and the hot beeswax are the same substance.
In addition, we use our reason to conclude that the people we see walking in the street are really people. From my third-story office window, all I see are colored images moving on the street. For all I know, the colored images are really nothing more than ghosts or robots, but my reason concludes that the moving color images are people because whenever I walk on the street, I meet people and not ghosts or robots. Once again, reason — not the senses — gives us knowledge.
Because of these things, Descartes concluded that the real source of knowledge is reason, not the senses. Descartes is therefore a Rationalist and not an Empiricist.
Conclusion: My Favorite Descartes Joke
Descartes was flying on an old-fashioned plane that has propellers. As you may know, if the propellers are turning at the right speed, they will look as if they have stopped although they are really going very fast. A fellow passenger looked out the window at the propellers, then tapped Descartes on the shoulder and asked, “Excuse me, but are those propellers moving?” Descartes looked out the window, and replied, “I think not.”
Then he disappeared.
Note: The quotations by Descartes that appear in this essay are from his book Meditations, translated by Laurence J. Lafleur.
Copyright by Bruce D. Bruce; All Rights Reserved
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