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).