Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Four Temperaments is a theory of psychology that stems from the ancient medical concept of humorism. It is equally important to consider the possibility that the four temperaments may not refer to personality but to mood. The distinction between mood and personality has largely been lost in modern psychology. Sanguine, Choleric, Melancholic and Phlegmatic might equally well refer to the moods of activity", "stressful anxiety", "sadness or depressed" and "calm or placidity". This interpretation of the four temperaments, allows the medical approach to the four humours to be better understood. Manipulation of the four humours was about changing the way people felt, rather than changing their personality type. One of the most popular today is the Keirsey Temperament Sorter, whose four temperaments were based largely on the Greek gods Apollo, Dionysus, Epimetheus and Prometheus, and were mapped to the 16 types of the Myers-Briggs Type Indicator (MBTI)."