小乘四门

Tiantai's division of Hīnayāna into four schools or doctrines:

(1) 有門 Of reality, the existence of all phenomena, the doctrine of being (cf. 發智六足論, etc.);

(2) 空門 of unreality, or non-existence (cf. 成實論);

(3) 亦有亦空門 of both, or relativity of existence and non-existence (cf. 毘勒論);

(4) 非有非空 of neither, or transcending existence and non-existence (cf. 迦旃延經).