Hadst thou not Greek enough to understand thus much: The end of Man is an Action and not a Thought, though it were the noblest.

Thomas Carlyle (1795-1881) Scottish essayist and historian

Sartor Resartus, Book 2, ch. 6 (1834)
    (Source)

From Aristotle, Nicomachean Ethics, 1.3.6 ("The end aimed at is not knowledge but action").

This chapter first appeared in Fraser's Magazine for Town and Country, Vol. 9, No. 51 (1834-03) -- Book 2, ch. 5-7.