Jean-Paul Sartre's Existentialism can be summarized with the following four points:
1. Existence precedes essence. That is, we humans are without a fundamental nature/essence. We find ourselves existent, completely blank, without a teleological(design), purpose(we make our own) or pre-destined future, with no over-arching similarities with one another, other than that we all have no fundamental essence. This is probably the biggest point, the ramifications of which follow. To fully describe the repercussions of this point would require much more time and energy.
2. Man is condemned to be free. We have no nature or inherent purpose, so it follows that there is nothing directly prescribed for our lives. We are completely responsible for our actions. We are wholly responsible for our actions and the cause of our actions. Sartre does not accept the excuse "it's only human nature" or anything of this sort. humanity's absolute freedom is directly opposite to the idea of pre-determination and fate (both which have a higher power as a pre-requisite). so it is either there is no god, or that if there is one, he/it does not concern itself with humanity and leaves it be.
3. Man is wholly responsible for his actions, and should act as if the rest of humanity would act in accord with his actions/choices. In this, we also bear a responsibility for all of mankind's actions. It is these obligations, in order to fully realize his freedom, that he uses this free will appropriately. Sartre would say that you and I are as responsible for the genocide in Sudan as are the people who are committing the murders; we should be doing something to stop it, Sartre would say. (On point, he was active in the French resistance during the Holocaust despite living in Paris under the Gestapo.)
4. The true existentialist lives the authentic life. Only when man recognizes the extent of his freedom and the obligations thereof can he live a fulfilling, meaningful life, in Sartre's view.
Interesting. Only, I find the idea of choosing for myself also bears the burden of choosing for all of mankind kinda absurd because I believe that man is end in himself. Existentialists claim that as all human beings within society are interdependent, one's actions necessarily affect other human beings and will create a domino effect on the community and an image that is "valid not only for you, but for our whole age."
Objectivisim, however, says that man must exist for his own sake, neither sacrificing himself to others nor sacrificing others to himself. With this in mind, I would like to raise a point of inquiry. To what extent, does an objectivist hold responibility for his actions?