The meaning and origin of the expression: The spirit of the staircase

The spirit of the staircase

What's the origin of the phrase 'The spirit of the staircase'?

'The spirit of the staircase' or, as it is often written, 'the spirit of the stairway', is one of those obliging phrases that has a definitive origin, in that it is a quotation from Denis Diderot's Paradoxe sur le Comédien, written 1773-78.

In the text Diderot retells a situation in which Jacques Necker makes a remark that perplexes him:

This confounds me and reduces me to silence, because the sensitive man, like me, overwhelmed, loses his head and finds himself at the foot of the stairs.

It is one of the few phrases that has come into English as a translation from the French. The original, which even my schoolboy French is up to translating, is 'L'esprit de l'escalier'. Most of the French phrases that have been adopted into English are used in their original French form, even the similar 'Esprit de corps'.

It isn't a commonly used phrase in the English-speaking world, which is a pity as it encapsulates a feeling that we must all surely have had.