"Cogito ergo sum." "Hell is other people." "Whereof one cannot speak, thereof one must remain silent.
These are three of the most quoted statements in the history of philosophy but, as Mike Rugnetta of PBS's Idea Channel notes, they're just as frequently misinterpreted.
1) Cogito ergo sum
This statement by French philosopher René Descartes — mostly commonly translated from the Latin as "I think, therefore I am" — is sometimes taken as a motivational, believe-in-yourself bit of pop psychology. But it's not. He's not saying, "If you think it, you can be it!" Nor is he claiming that if you have thoughts, you must therefore have a physical brain and body.
What he means is thinking requires a thinker — which seems pretty self-evident — and the fact that a thought is thought proves the existence of that thinker. "For Descartes," says Rugnetta, "the cogito is a first order of knowledge," which means all other knowledge is premised upon the fact that there is a knower to know stuff.
2) Hell is other people
No, this does not mean other people are the worst and you should hide yourself in a dark, lonely room so that you don't have to put up with them. The line comes from a 1944 existentialist play by French philosopher Jean-Paul Sartre called Huis Clos, or No Exit. In the play, three people are trapped in Hell — which is a single room — and ultimately, while confessing their sins to one another, end up falling into a bizarre love triangle.
The confinement of the characters extends beyond their physical holding room: they are trapped by the judgments of their cellmates. That's why one of the characters says, "Hell is other people" — because of how we are unable to escape the watchful gaze of everyone around us. "By there mere appearance of the Other," says Sartre in Being and Nothingness, "I am put in the position of passing judgment on myself as on an object, for it is as an object that I appear to the Other."
Sartre offered a clarification about his much misunderstood phrase:
"Hell is other people" has always been misunderstood. It has been thought that what I meant by that was that our relations with other people are always poisoned, that they are invariably hellish relations. But what I really mean is something totally different. I mean that if relations with someone else are twisted, vitiated, then that other person can only be hell. Why? Because … when we think about ourselves, when we try to know ourselves … we use the knowledge of us which other people already have. We judge ourselves with the means other people have and have given us for judging ourselves.
As Rugnetta explains: "Hell is other people because you are, in some sense, forever trapped within them, subject to their apprehension of you."
3) Whereof one cannot speak, thereof one must be silent
This line from Ludwig Wittgenstein is often used to mean, "If you don't know what you're talking about, then shut up." But as Rugnetta explains, the German philosopher intended something more abstract.
Wittgenstein was interested in the relationship between language and reality, and the ways in which the former is capable of representing the latter. Ultimately, he argued, we can't have knowledge of aspects of reality that aren't representable through language. We cannot speak of them, and therefore cannot claim knowledge about them.
Confused? Watch the video above and see if that helps.