Each man's master is the person who has the authority over what the man wishes or does not wish, so as to secure it, or take it away.
Of all existing things some are in our power, and others are not in our power. In our power are thought, impulse, will to get and will to avoid, and, in a word, everything which is our own doing. Things not in our power include the body, property, reputation, office, and, in a word, everything which is not our own doing.