But indeed Conviction, were it never so excellent, is worthless till it convert itself into Conduct. Nay properly Conviction is not possible ill then.

Thomas Carlyle (1795–1881) Scottish essayist and historian

Sartor Resartus, Book 2, ch. 9 (1834)
    (Source)

Quoting Herr Teufelsdröckh.

This chapter first appeared in Fraser's Magazine for Town and Country, Vol. 9, No. 52 (1834-04).