Cogito, ergo sum facts for kids

The famous Latin phrase cogito, ergo sum means "I think, therefore I am". It's a key idea from the French philosopher René Descartes. He first wrote it in French in his 1637 book, Discourse on the Method. He wanted more people to understand it, so he wrote it in French instead of just Latin. Later, it appeared in Latin in his Principles of Philosophy.

This idea became a very important part of Western philosophy. Descartes used it to find something he could be absolutely sure about. He believed that even if everything else could be a dream or a trick, the very act of doubting proved that he, as a thinking person, must exist. If you are doubting, then there must be a "you" doing the doubting!

Some people, like Pierre Gassendi, have pointed out a small problem with this idea. They say that Descartes should have just said "thinking is happening" instead of "I am thinking." This is because saying "I am thinking" already assumes there is an "I" (a person) doing the thinking.

Descartes's Big Idea

Descartes first shared his famous phrase in his 1637 book, Discourse on the Method. He wrote it in French as je pense, donc je suis.

He explained that our senses can sometimes trick us. Also, people can make mistakes even when thinking about simple things like math. He even thought that our waking thoughts could be like dreams. So, he decided to pretend that everything he had ever thought was false.

But then he realized something important. Even if he was pretending everything was false, he, the one doing the thinking, had to exist. He wrote that the truth, "I think, therefore I am," was so strong that no doubt could shake it. He decided this was the first basic truth of his philosophy.

Later, in his 1641 book Meditations on First Philosophy, he wrote something similar in Latin: "I am, I exist, whenever I say it or think it, is necessarily true."

In his 1644 book Principles of Philosophy, the full Latin phrase "ego cogito, ergo sum" appeared. He explained that we cannot doubt our own existence while we are doubting. This is the first thing we learn when we start to think deeply about philosophy.

Descartes also wrote in another work that his idea could also be expressed as dubito, ergo sum ("I doubt, therefore I am"). He said this meant the same thing as "I think, therefore I am."

Older Similar Ideas

Even though "I think, therefore I am" is linked to Descartes, similar ideas were around long before him.

For example, the ancient Greek philosopher Plato talked about "knowledge of knowledge." And Aristotle explained that when we see, we know we are seeing. When we think, we know we are thinking. He said that being aware of our thoughts and perceptions means we are aware that we exist.

Around 400 AD, Augustine of Hippo, a famous Christian philosopher, wrote something very similar. In his book De Civitate Dei, he said: "If I am mistaken, I exist." This means that even if he was wrong about everything, the fact that he could be wrong proved he existed. This is sometimes called the Augustinian cogito.

Descartes actually knew about Augustine's idea. He wrote that he was happy to agree with Augustine, especially because it helped silence people who criticized his own idea. However, Descartes used the idea to show that the "I" that thinks is a non-physical mind, not a body. Augustine used it to show a likeness of the Trinity in humans.

Another similar idea came from Avicenna, an Islamic philosopher. He had a "Floating Man" thought experiment. He imagined a person floating in the air, unable to see or feel anything. Even in this state, the person would still be aware of their own existence.

What People Think About It

Descartes's idea has been discussed and debated a lot.

The "I" Problem

One of the main criticisms, first brought up by Pierre Gassendi, is about the word "I." Critics like Georg Christoph Lichtenberg and Friedrich Nietzsche argued that Descartes should have said "thinking is happening" instead of "I am thinking." They believed that saying "I am thinking" already assumes there is a specific "I" (a person) doing the thinking.

They suggest that the phrase implies too much. The fact that thoughts exist doesn't automatically mean there's a specific "I" or person behind them. Nietzsche even joked that a better phrase might be "it thinks," like saying "it is raining," where "it" doesn't refer to a specific person.

Is it too simple?

The Danish philosopher Søren Kierkegaard called the phrase a tautology. This means it's a statement that is true by its own definition. He argued that "I think" already assumes that "I" (a person) exists. So, saying "therefore I exist" is just repeating what was already assumed. For Kierkegaard, existence is something that must be true for thinking to even happen in the first place.

See also

• Cartesian doubt
• Floating man
• Solipsism
• Brain in a vat
• I Am that I Am
• Tat Tvam Asi, "You are that"