""To divide philosophy into four." Matter was divided into four elements and therefore philosophy had to be divided into four parts. This division into four was described as the series of the four colors: nigredo, i.e., darkness; albedo, i.e., the ascent of light, becoming light; citrinatis, i.e., becoming yellow, and finally the strange color suggested by the Greek word "iosis": "becoming iosis." Berthelot sometimes translated it as violet, but that is questionable."

- ~Carl Jung, Psychology of Yoga and Meditation, Page 155-156