Causes neither internal nor external

Also neutral cause. One of the three causes of disease posited by Sān Yīn Jí Yī Bìng Zhèng Fāng Lùn (三因极一病症方论 Unified Treatise on Diseases, Patterns, and Remedies According to the Three Causes). It includes dietary irregularities, taxation fatigue, knocks and falls, and animal and insect bites. See cause of disease; three causes.