The Littauers, like many Christian psychologists, rely heavily upon the so-called Four Temperaments. This long-discredited personality theory evolved from the ancient Greek belief that the physical realm was composed of four elements: earth, air, fire, and water. Empedocles related these to four pagan deities, while Hippocrates tied them to what were considered at that time to be the four bodily humors: blood (sanguine), phlegm (phlegmatic), yellow bile (choleric), and black bile (melancholy). These characteristics were further connected to the signs of the zodiac.