The School of Naturalists or the School of Yin-Yang (simplified Chinese: 阴阳家; traditional Chinese: 陰陽家; pinyin: Yīnyángjiā; Wade–Giles: Yin-yang-chia; lit. 'School of Yin-Yang') was a Warring States-era philosophy that synthesized the concepts of yin-yang and the Five Elements. It was one of the Nine Schools of Thought.