Existentialism is summarized in one phrase, "existence precedes essence." But what does this mean? Pre-existentialism, philosophical systems presumed Man had an essence. To understand what that means consider a chair. Chairs don't just randomly pop into existence. Before they are created someone or something has to have a concept of what a chair is (i.e., something for sitting), then the chair is created in conformity with the concept. The essence of a chair is that for which it is designed.
Notice two things: (a) having an essence, in the sense I've described, implies a creator and that the creation's essence is determined before it comes into existence. And so, artifacts--things like chairs, computers, cars, iphones, etc--all have creators and have an essence/nature/purpose before they come into existence.
Let's return to "existence precedes essence." For existentialists, human beings are unlike artifacts in that we exist before we have an essence/nature. We are not designed and so there is no predetermined essence that defines who or what we are. Who we are comes after we exist. We are thrust into the world and create ourselves through the actions we choose. This is what "existence precedes essence" means: first we exist, then we will acquire a nature (though our acts). If I do harmful acts and act selfishly, then this is what I am. If I create and share, then this is my nature. There is no nature beyond what I actually do. Again, contrast this with artifacts: first they have a nature/essence/purpose then they are brought into the world.
For existentialists, the human condition is understanding that we are free to choose our own essence and figuring out how we ought to create ourselves given we have no intrinsic nature.
Radical Freedom and Responsibility
Although we have no common nature among us we all share the same conditions: We are "condemned" to be free yet we have to make choices about how to live and 'be'. There is nothing objective in the world to clutch to guide us in our choices. Every choice is exactly that--our choice. And because every action is a consequence of our own choice, we bear absolute responsibility for it. Pretending you don't have a choice is what Sartre calls "bad faith". You are denying the reality of your radical freedom but you cannot escape responsibility for your choices which define who you are.
Now some might say that we can turn to religion or authorites to guide us. There are a few problems with this. First, you are shirking your responsibility as a free being for decisions. By deferring to an outside source for your decisions your are denying your responsibility to choose for yourself. One might say that choosing to follow this or that text or leader is a choice--and it is. But how you choose to interpret the various texts and advice will also be a matter of your own choice. You cannot escape the subjectivity of your existence and so you still must bear the responsibility of choosing one interpretation over another.
Furthermore, your essence is nothing more that the sum of the things that you do. And if trying to deny your radical freedom and offload responsibility are part of your actions, then you are a coward. Anguish, for the existentialist, in part comes from knowing that he bears full responsibility for what he does and who he is.
If there are no objective values in the world, it seems like anything goes. Again, just like with any other choice, the ethics that you choose define your essence. If you choose and act on a selfish ethic, then that's what you are and you are responsible for everything that comes from it.
But our actions aren't completely unconstrained. Here's where we exit subjectivity. Every choice that I make not only defines who I am but also defines the essence of Man as a whole because I am a part of that whole. This demands that I consider the consequences of my choices on what will be the nature of Man.
For every man, everything happens as if all mankind had its eyes fixed on him and were guiding itself by what he does. And every man ought to say to himself "Am I really the kind of man who has the right to act in such a way that humanity might guide itself by my actions?
I am responsible, through my choices, for how Man is defined for my time in history because I am a part of Man.
But this is vague? How do I decide what to do in specific cases? Unfortunately, general moral principles can't tell us how to decide particular cases. Sartre give the following case:
[The young man's] father was on bad terms with his mother, and, moreover, was inclined to be a collaborationist; his older brother had been killed in the German offensive of 1940, and the young man, with somewhat immature but generous feelings, wanted to avenge him. His mother lived alone with him, very much upset by the half-treason of her husband and the death of her older son; the boy was her only consolation. The boy was faced with the choice of leaving for England and joining the Free French Forces--that is, leaving his mother behind or remaining with his mother and helping her to carry on.And so a general ethic principle can't help us decide specific cases. And besides, even if we do choose a general ethical principle, there is no guide to tell us which to choose. We also have to make that choice and we bear responsibility for it and accept that it now defines us in so far as we act on it.
He was fully aware that the woman lived only for him and that his going off--and perhaps his death--would plunge her into despair. He was also aware that every act that he did for his mother's sake was a sure thing, in the sense that it was helping her to carry on, whereas every effort he made toward going off and fighting was an uncertain move which might run aground and prove completely useless; for example, on his way to England he might, while passing through Spain, be detained indefinitely in a Spanish camp; he might reach England or Algiers and be stuck in an office at a desk job. As a result, he was faced with two very different kinds of action: one, concrete, immediate, but concerning only one individual; the other concerned an incomparably vaster group, a national collectivity, but for that very reason was dubious, and might be interrupted en route. And, at the same time, he was wavering between two kinds of ethics.
On the one hand, an ethics of sympathy, of personal devotion; on the other, a broader ethics, but one whose efficacy was more dubious. He had to choose between the two. Who could help him choose? Christian doctrine? No. Christian doctrine says, "Be charitable, love your neighbor, take the more rugged path, etc., etc." But which is the more rugged path? Whom should he love as a brother? The fighting man or his mother? Which does the greater good, the vague act of fighting in a group, or the concrete one of helping a particular human being to go on living? Who can decide a priori? Nobody. No book of ethics can tell him. The Kantian ethics says, "Never treat any person as a means, but as an end." Very well, if I stay with my mother, I'll treat her as an end and not as a means; but by virtue of this very fact, I'm running the risk of treating the people around me who are fighting, as means; and, conversely, if I go to join those who are fighting, I'll be treating them as an end, and, by doing that, I run the risk of treating my mother as a means.
Sartre and Emotions
General ethical principles can't tell me what to do in particular cases. Maybe I ought to do what feels right to me. If the young man feels that his love for his mother is great enough to sacrifice his other desires, then he should do that. But if the feeling of love for his mother isn't enough to make him give up everything else, then he ought to leave.
But how will he know that he loves his mother enough to give up everything else unless he actually does it? To know that his feeling leads him to the right choice he has to live that choice. He has to see how it plays out. He might try it and find out that the desire to avenge his brother overwhelms him and he's unhappy staying behind. But he can't know this before he lives it. The feeling can't tell him in advance what to do.
Consider another case that many can relate to. How do you know if marrying someone will be the right choice? Consulting your feelings before you're married can't tell you. You'll only know if it's the right choice if you actually do it. If it turns out well, it was the right choice. If it turns out poorly, it wasn't. The feeling can't tell you what's going to happen. If feelings were a good guide to marriage, we'd expect the divorce rate to be substantially lower.
It Isn't All Doom and Gloom
So, we are hurled into the world, condemned to be free with no fixed lights to guide us in how we ought to live, yet we are somehow responsible for everything we do and are. This is the existential forlornness and anguish. Forlorn because we cannot turn to anyone to make decisions for us and anguish because of the tremendous responsibility that comes with creating both our own essence and that of Man.
But chin up butter cup! The good news is that existentialism is a philosophy of action. You might not have any guides but you get to create yourself--with every choice. Bonus, if you didn't like where things were going, you can reinvent yourself at any moment, if you so choose.
There is no reality except in action. Man is nothing else but his plan; he exists only to the extent that he fulfills himself; he is therefore nothing else than the ensemble of his acts, nothing else than his plan.Before you go skipping off into the sunset, existentialism is a demanding philosophy if you take it seriously. In creating yourself and defining Man, with every act you are saying "this is what I think all mankind ought to be--follow me!" When taken seriously, that is a massive responsibility to bear.
It also means that there is nothing that exists that is not expressed in action. There are great authors with unwritten great books, no charitable people with kind deeds undone, no great loves who have not loved. "Reality alone counts and [...] dreams, expectations, and hopes warrant no more than to define a man as a disappointed dream, miscarried hopes, as vain expectations." In other words, coulda woulda shoulda is worthless. At the end of the day, what matters is what you did with your life and whether it was an example for others to follow.