It is also called Hinayana and it advocates the necessity of attaining enlightenment of Kuri (abstract or impracticable theory) in order to renounce worldly desires but as it regards every substance as a part of Ku (mind that is not bound by anything), it is called 'Tanku-no ri' (the theory of only Ku) or 'Henshin no Kuri' (the abstract or impracticable theory of prejudicial truth) because it is a prejudiced truth.
小乗教ともいい煩悩を断ずるために、空理を悟るべきことを説くが、すべての実体をただ空の一辺のみと見るので「但空（たんくう）の理」といい、また偏った真理なので「偏真の空理」ともいう）