No iron chain, or outward force of any kind, could ever compel the soul of a man to believe or to disbelieve: it is his own indefeasible light, that judgment of his; he will reign, and believe there, by the grace of God alone!

Thomas Carlyle (1795-1881) Scottish essayist and historian

Lecture (1840-05-15), “The Hero as Priest,” Home House, Portman Square, London
    (Source)

The lecture notes were collected by Carlyle into On Heroes, Hero-Worship, & the Heroic in History, Lecture 4 (1841).