If you're reading these words, you've at least heard about the Enneagram. Maybe you overheard friends or coworkers describing people using numbers: “She's such a Four,” or “You have to expect that from an Eight.” You probably thought they were discussing numerology, astrology, the tarot, or, if you had a background in psychology, the Myers-Briggs Type Indicator. Whether you were irritated or intrigued — or both — this chapter will introduce you to an ancient system that has evolved into a modern tool for understanding human personality.