Great men, and great actions, are seldom wasted; they send forth a thousand unseen influences, more effective than those which are seen
 John Stuart Mill, A System Of Logic, Ratiocinative And Inductive (1843). copy citation

Context

“It must not be concluded that the influence of either is small, because they can not bestow what the general circumstances of society, and the course of its previous history, have not prepared it to receive. Neither thinkers nor governments effect all that they intend, but in compensation they often produce important results which they did not in the least foresee. Great men, and great actions, are seldom wasted; they send forth a thousand unseen influences, more effective than those which are seen; and though nine out of every ten things done, with a good purpose, by those who are in advance of their age, produce no material effect, the tenth thing produces effects twenty times as great as any one would have dreamed of predicting from it.” source