The greatest of faults, I should say, is to be conscious of none.

Thomas Carlyle (1795-1881) Scottish essayist and historian

Lecture (1840-05-08), “The Hero as Prophet,” Home House, Portman Square, London
    (Source)

The lecture notes were collected by Carlyle into On Heroes, Hero-Worship, & the Heroic in History, Lecture 2 (1841).