“For when all is said and done, could it be that what frightens them about the doctrine that I shall try to present to you here is that it offers man the possibility of individual choice?”

Sartre’s detractors accused his existentialism of being too pessimistic, but he claims that those same detractors are also prone to explaining morally repugnant acts as “human.” The suggestion here is that we cannot excuse moral failures by treating them as the inevitable results of a flawed human nature. Existentialism holds that a person is always responsible for his actions and is always free to choose any action he likes. Sartre considers this doctrine deeply optimistic but suggests that his critics might be frightened by the responsibility that it implies. 

“The truth is that of all doctrines, this is the least scandalous and the most austere: it is strictly intended for specialists and philosophers.” 

This statement occurs just after Sartre has enumerated a number of silly misunderstandings of existentialism he has seen in the popular press and expresses the frustration he seems to have felt at being called to account for his philosophy before people who had never read it, much less understood it. No doubt some of Sartre’s leftist critics found his elitism and separation of the philosophical from the general and political a further cause for their disapproval. 

“If God does not exist, there is at least one being in whom existence precedes essence—a being whose existence comes before its essence, a being who exists before he can be defined by any concept of it.” 

Sartre’s reasoning here is as follows: human beings were not created by a God who endowed them with a certain essence, nor does instinct dictate all our actions; we are essentially free, and the choices we make (about which projects to pursue, which values to uphold, and so on) make us who we are.