Jean-Paul Sartre (born 21 June, 1905; died 15 April, 1980), pictured above as a young man
'First, what do we mean by anguish? – The existentialist frankly states that man is in anguish. His meaning is as follows: When a man commits himself to anything, fully realising that he is not only choosing what he will be, but is thereby at the same time a legislator deciding for the whole of mankind – in such a moment a man cannot escape from the sense of complete and profound responsibility. There are many, indeed, who show no such anxiety. But we affirm that they are merely disguising their anguish or are in flight from it. Certainly, many people think that in what they are doing they commit no one but themselves to anything: and if you ask them, “What would happen if everyone did so?” they shrug their shoulders and reply, “Everyone does not do so.” But in truth, one ought always to ask oneself what would happen if everyone did as one is doing; nor can one escape from that disturbing thought except by a kind of self-deception. The man who lies in self-excuse, by saying “Everyone will not do it” must be ill at ease in his conscience, for the act of lying implies the universal value which it denies. By its very disguise his anguish reveals itself. This is the anguish that Kierkegaard called “the anguish of Abraham.” '
—from Existentialism is a Humanism (1946; translated from the French by Philip Mairet)