Jean-Paul Sartre said this quote
“ He walked on in silence, the solitary sound of his footsteps echoing in his head, as in a deserted street, at dawn. His solitude was so complete, beneath a lovely sky as mellow and serene as a good conscience, amid that busy throng, that he was amazed at his own existence; he must be somebody else's nightmare, and whoever it was would certainly awaken soon. ”