Here is the set up.
One day during the Occupation, Sartre said, an ex-student of his had one to him for advice. The young mans’s brother had been killed in battle in 1940, before the French surrender; then his father had turned collaborator and deserted the family. The young man became his mother’s only companion and support. But what he longed to do was sneak across the border via Spain to England, to join the Free France forces in exile and fight the Nazis —red-blooded combat at last, and a chance to avenge his brother, defy his father, and help to free his country. The problem was, it would leave his mother alone in danger at a time when it was hard even to get food on the table. It might also get her into trouble with the Germans. So: should he do eat right thing by his mother, with the clear benefits to her alone, or should he take a chance on joining the fight and doing the right by many? … Before coming to Sartre, the student had though of seeking advice from the established moral authorities…
This involved the student searching for a master (S1), such as religious leaders, books by poets and philosophers, his own ‘inner voice’ (i.e. the internalized Other, the superego) to the extent that this was possible.
The student knew all of these masters (S1) would fail, and therefore he appealed to his former teacher/master (S1) Sartre. Why Sartre? Because, if nothing else, Sartre would not give him a stock answer that was nothing more than a packaged banal cliches.
Sure enough, Sartre listened to his problem and said simply, ‘You are free, therefore choose —that is to say, invent’ No signs are vouchsafed in this world, he said. None of the old authorities can relieve you of the burden of freedom. You can weigh up moral or practical considerations as carefully as you like, but ultimately you must take the plunge and do something, and it’s up to you what that something is.
I would say that Sartre recognized the student was engaging in the discourse of the hysteric, where the subject ($) demands that the master (S1) produce the knowledge (S2) that will “free” the subject to act without anxiety. The hysteric seeks the master that will give them their desired object or experience (a).
Of course, Sartre knew that no master (S1) can ever give the subject ($) what the subject desires (a).
Thus Sartre engaged in the discourse of the analyst, where Sartre became (a), which is to say the eluded the student’s attempt ($) to turn him into the master (S1). By doing this Sartre was helping the student authorize his own actions.
To drive the point home by continuing the discourse of the analyst with the audience…
Sartre doesn’t tell us whether the student felt this was helpful, nor what he decided to do in the end.
— Source I’m quoting from in this post: Sarah Bakewell, _The Existentialist Café_