"The mind of man is capable of anything"
Guy de Maupassant
Public DomainGuy de Maupassant - Credit: Gaspard-Félix Tournachon

Several critics have suggested this sentence may have been taken from the closing line of Guy de Maupassant's short story 'Le Chevelure' ('A Tress of Hair'): 'L'espirit de l'homme est capable de tout.'


Further reading:

Joseph Conrad, 'Guy de Maupassant' (1904)

Yves Hervouet, The French Face of Joseph Conrad (1990)