Great cities are not like towns, only larger. They are not like suburbs, only denser. They differ from towns and suburbs in basic ways, and one of them is that cities are, by definition, full of strangers.
Petrus Comestor saith that Mount Olympus riseth even to the clear aether, wherefore letters written in the dust on the summit of that mountain have been found unchanged after the lapse of a whole year. Neither can birds live there, by reason of the rarefaction of the air, nor could the Philosophers who have ascended it remain there even for a brief space of time, without sponges soaked in water, which they applied to their nostrils and sucked thence a denser air.