Laws are coldly reasoned out and established upon what the lawmakers believe to be a basis of right. But customs are not. Customs are not enacted, they grow gradually up, imperceptibly and unconsciously, like an oak from its seed. In the fullness of their strength they can stand up straight in front of a world of argument and reasoning and yield not an inch.

Mark Twain (1835-1910) American writer [pseud. of Samuel Clemens]

Essay (1906), “The Gorky Incident,” Letters from the Earth (c. 1909; pub. 1962) [ed. DeVoto (1939)]
    (Source)

Commenting on the eviction of Maxim Gorky from multiple hotels in New York City because the woman he was traveling with was not his wife. Twain was a supporter of Gorky's efforts to foment revolution in Tsarist Russia.

The essay was not published in Twain's lifetime. It's original publication was in the Slavonic and East European Review (1944-08), also edited by DeVoto.