Existence is everything and nothing. How do we know we exist? Or even better, how do we know that other people exist? Something so basic as existence should be obvious, but is it really? 

We don’t tend to wonder if our body is real, if the aches and pains we experience as human beings are facts or just perceptions from outside ourselves. We are sure that you didn’t question that last enjoyable meal you had and how you were able to experience it. How do we know that we exist as such?

This is where our dude René Descartes, a 17th century philosopher and mathematician, comes in. Descartes, one of the most iconic thinkers of modern philosophy, decided to do a thought experiment.

It was clear that this Frenchman had spent a lot of time thinking. So he decided that he would take his thoughts back to the very, very basics. He would doubt everything that he believed to be true and see if he could work his way back.

First, he would doubt the existence of others, then he would doubt the existence of himself, and furthermore, assume he was being tricked into believing he (and others) existed by some trickster demon. 

From there, our boy René builds it back up. He starts off with the assumption of a benevolent creator, then comes to the realization, “Je pense donc je suis,” or, as it was written in the lingua franca at the time, Latin: “Cogito ergo sum.” I think therefore I am.

But what does this mean? The Cartesian Cogito, as the phrase is often called, comes out of the idea that the human essence is mind, and that there is a dualism between body and mind, but the two interact in a way that makes us do the cool (and sometimes stupid) actions of daily living.

In Descartes’s philosophy, he knows that he exists because he’s able to think and reason, and his mind is the foundational evidence of his existence. His body could be some automaton, but what makes us human is our ability to think.

Where does that leave everyone else, though? How do we know other people or other minds exist? Well, that is a question for another time, one that 20th century Analytic philosophers such as Fred Dretske liked to address in more complicated ways.

However, there is a lot of criticism of this mind/body dualism perspective. If we are some disembodied mind, how does our body function? Aren’t we embodied beings? Don’t we experience things in terms of embodied experience? If the body ceased existing, would the mind still exist outside of it?

Do you exist? Well, feel free to honk your car horn, bicycle horn, or party horn if you think you do.