At long last, we're returning to existentialism after an initial foray into it with Camus. We've previously covered Sartre talking about phenomenology and the self, and also Kierkegaard talking about the self and values, so those are related, as is Heidegger's talk about being-in-the-world and our proper attitude towards Being. Oh, and Buber also talked about the primacy of "the Other" in making sense of ourselves, and this general discussion of "self" continued in many of the above and was key in one of our Hegel episodes.
"Existentialism" is an amorphous term that is used in many ways; it connotes primarily the experience of me, now, facing life, including my own death. Well, that's pretty much one end of philosophy, isn't it, or rather the center, where the periphery is made up of various subjects that we throw ourselves into, studying them with some analytical apparatus like that of science, or history, or mathematics. Any time philosophy becomes urgent, becomes about facing the human condition and trying not to be distracted or otherwise self-deceived, then you're talking about existentialism, so it's not surprising that you could have Christian existentialists and Buddhist existentialists... ones that emphasize being-unto-death and those that on the other hand emphasize living live fully in the face of death (in this case, there's kinship to romanticism). Some of the most famous philosophers described as part of the historical movement of "existentialism" didn't themselves accept that appellation, perhaps because of that very amorphous and consequently shallow way that the term was tossed around as a cultural movement.
Sartre, for a while at least, willingly adopted the term, and in "Existentialism as Humanism" characterized it in a way easy for people to understand and repeat: "existence precedes essence." Taken literally, this means there is no human nature: there is no human "essence." But of course, there are facts about us that can be and are recorded: anthropology isn't based on an illusion. Sartre's claim is not about the science of psychology but about how we experience ourselves, and the upshot is that we--as thinking, acting beings--are a spontaneity. Even though I can look at your behavior and say "I knew you would do that based upon your character," that's not how we experience things ourselves; we always feel (if we're honest with ourselves, an important qualification) that we could have done something differently, and Sartre thinks the same even goes for how we react emotionally, how we judge things. Yes, there are objective things in the world that present barriers to action, e.g. maybe I have a disability, but those things simply serve as the raw medium by which we ourselves create our worlds: I can see my disability as a challenge, or as a nuisance, or my cross to bear, or an undeserved affliction. This freedom to interpret the world does not take place in a vacuum as if I were creating a fantasy world from scratch, but just as in action, when I can choose this or that path, the objective matter of the world gives me choices re. what I'll even call a "path."
To use Heidegger's term, these objective things about me are my "facticity," but we shouldn't acknowledge as primary this distinction between the brute given in my experience (e.g. the fact of my disability) and the stance I (freely, according to Sartre) take towards this given. As we've emphasized in many podcasts, there is no such thing as a brute given: being-in-the-world is our primary experience, and even the talk of consciousness vs. the world is a matter of creating abstractions that end up distorting this experience. The upshot is that despite (or because of) facticity, despite "my character" being an object in the world (visible to others really much more directly than I'm visible to myself) built over time as I perform actions, I'm still responsible for my own situation: it's "my fault" that I am who I am with the attitude and reputation that I have, despite this not having been a matter of deliberation on my part, and despite there being a lot of apparent luck involved in my ending up where I am.
So that's the crux. Sartre emphasizes this freedom as the central existential challenge: we are "condemned to be free" whether we like it or not, not only because our actions and world-interpretations are ours (from our own point of view, and he things we have to attribute such freedom to other people as well), but because the is-ought distinction makes no moral rules binding on us: even if God Himself came up and told you to do something, that would not define "good" for you (see our discussion of Plato's "Euthyphro" for a lot more on this); there would still be that free act of interpretation on your part to accept his command as establishing a value. That's the way the creation of values that Nietzsche talked about works: when I do something, or even affirm it with my attitude, I'm creating a value right then, I'm acting as a model for everyone else and proclaiming it to be objectively good.
But can't I do things that I know to be wrong? Well, if I think I'm doing that, then what I'm really doing is affirming something with one hand while denying it with the other: I'm contradicting myself, and I'll realize that if I stop playing games and denying my own freedom and responsibility. So that's what "bad faith" (Kaufmann translates it as "self-deception) amounts to: I'm denying my own freedom/responsibility, either by thinking of myself as determined ("I couldn't help it. That's just the way I am") like an object or by denying that I've really built myself up to be the person that I am ("I'm not a cheater just because I cheat sometimes!").
In No Exit, three characters trapped in hell (literally) torture themselves endlessly as a result of their own bad faith: they like things in certain ways and won't admit that they themselves are responsible for their likes and dislikes being the way the are (so they therefore won't let themselves change to adapt to their new surroundings). They each have psychological and emotional needs that can't be satisfied by their companions and again are unable (Sartre would say unwilling) to take responsibility for these needs and work to change them. One of them (Garcin) claims that he died too young to "do his deeds;" he claimed all his life that he was brave and presented himself as a brave opinion-maker, but this self-image contradicted his actual actions when bravery was actually called for. As one would expect from good art, the vividness of the depiction makes the play more than just a series of exemplars for bad faith, and it's not really even made explicit how Sartre would like these people to act instead.
Sartre (in "Existentialism is a Humanism") cited this overall feeling of depression that people come away with from existentialist literature as a reason to make the doctrine explicit, to show that it was life-affirming, morally responsible, and not at all nihilistic. Whether in trying to do this he ended up with an overly simplistic account that fails to do justice to our moral reasoning and self-awareness is something we will hopefully discuss.
You can read all three works online for free: "Existentialism is a Humanism", "Bad Faith" (part 1, chapter 2 of Being and Nothingness) (p. 47-72), and No Exit.
You can also buy the first two of these selections along with a lot of other great existentialist texts in Walter Kaufmann's Existentialism from Dostoevsky to Sartre and purchase No Exit and Three Other Plays.