But Sartre found that the US’ official embrace of individualism masked a parochial conformism. This is literally made concrete in New York’s regimented grid of numbered streets that ‘look so much alike that they have not been named’.

Of its typical citizen he wrote, ‘it is when he is acting like everyone else that he feels most reasonable and most American; it is in displaying his conformism that he feels freest.’ For Sartre, freedom was about the individual taking responsibility for their actions and challenging the government. American freedom was little more than exercising consumer choice while remaining fiercely loyal to the flag. The philosopher of freedom and the land of the free found themselves at cross purposes.

That helps explain why Sartre thought, paradoxically, that ‘never were we freer than under the German occupation’. Under their oppressive occupiers the French were forced to recognise that everything they did was a choice with potentially fatal consequences. In an America that felt safe and free, people took their liberty for granted and forgot how to truly exercise it.

That is perhaps why, after decades of peace, American freedom has come to Paris. Fifty years ago this month, you’d have seen Sartre on the Left Bank making speeches and handing out newspapers in support of the student-led strike that almost brought down the government. Those streets today are full of high-class galleries, boutiques and restaurants: an ostentatious temple of consumer choice rather than a sober cloister of true existential freedom.