Oliver Wendell Holmes, Jr.‘s image of intellectual heroism:
No man has earned the right to intellectual ambition until he has learned to lay his course by a star which he has never seen — to dig by the divining rod for springs which he may never reach. In saying this, I point to that which will make your study heroic. For I say to you in all sadness of conviction, that to think great thoughts you must be heroes as well as idealists. Only when you have worked alone — when you have felt around you a black gulf of solitude more isolating than that which surrounds the dying man, and in hope and in despair have trusted to your own unshaken will — then only will you have achieved. Thus only can you gain the secret isolated joy of the thinker, who knows that, a hundred years after he is dead and forgotten, men who never heard of him will be moving to the measure of his thought — the subtile rapture of a postponed power, which the world knows not because it has no external trappings, but which to his prophetic vision is more real than that which commands an army.
From page 60 of Louis Menand’s The Metaphysical Club: A Story of Ideas in America. Emphasis mine.