People seem to like organizing and categorizing things, including themselves. Hippocrates wrote of the Four Temperaments, Myers and Briggs published MBTI in the 1940s, and a modern version of the Enneagram of Personality has become popular in recent years. (One of my favourite books on personality types is The Treasure Tree.) I have my own theory when it comes to the workplace; that most people's motivations can fit them into one of two categories: True Believers and Mercenaries. Understanding your coworker’s, supervisor’s, and staff’s motivations can help you understand and predict their actions, and hopefully ease frustrations when they do things opposite of what you would choose.