A primary theme in the works of Friedrich Nietzsche is the duality of master and slave morality. His master morality can be summarized in Ralph Waldo Emerson’s declaration in Self-Reliance that “virtue is Height.” Nietzsche says that slave morality is essentially a psychological trick used by the lower castes of society to take revenge on the nobility for being better than they are. It can be seen that Kurtz from Joseph Conrad’s novella Heart of Darkness is an adherent of master morality rather than slave morality.