Small men, most active, useful, are to be seen everywhere, whose whole activity depends on some conviction which to you is palpably a limited one; imperfect, what we call an error.
 Thomas Carlyle, On Heroes, Hero-Worship, and The Heroic in History (1841). copy citation

Context

“At all seasons of his history he must have felt, among such people, how, if he explained to them the deeper insight he had, they must either have shuddered aghast at it, or believing it, their own little compact hypothesis must have gone wholly to wreck. They could not have worked in his province any more; nay perhaps they could not now have worked in their own province. It is the inevitable position of a great man among small men. Small men, most active, useful, are to be seen everywhere, whose whole activity depends on some conviction which to you is palpably a limited one; imperfect, what we call an error. But would it be a kindness always, is it a duty always or often, to disturb them in that? Many a man, doing loud work in the world, stands only on some thin traditionality, conventionality; to him indubitable, to you incredible:” source