이 교 (敎)는 비록 같이 여환즉공 (如幻卽空)의 뜻을 세우나, 네 사람의 관법 (觀法), 곧 관찰하는 방법이 네 가지로 서로 같지가 않다
첫째는 유문 (有門) 또는 실문 (實門). 이는 여환즉공 (如幻卽空)이란 유즉공 (有卽空)이며 공즉유 (空卽有)로, 이 중 공즉유( 空卽有)로써 도 (道)에 들어가는 것을 말함.
다음은 공문 (空門) 또는 부실문 (不實門)으로, 유즉공 (有卽空)으로써 도 (道)에 들어가는 것.
셋째는 역유역공문 (亦有亦空門) 또는 역실역부실문 (亦實亦不實門)으로, 공 (空)과 유 (有)를 서로 비추어 도 (道)에 들어가는 것.
마지막은 비유비공문 (非有非空門 )또는 역실역부실문 (亦實亦不實門)으로, 환유 (幻有)도 환공 (幻空)도 얻지 못하므로 공( 空)과 유 (有)를 다 버림으로써 도 (道)에 들어가는 것을 말함.

The four gates of pervasive teachings: The four gates accord in principle with the theory that all the phenomena in the whole universe is but the emptiness of illusion, yet each of their four approaches varies in the achievement of the Way.
The first view is the door of reality or existence. It argues that "illusion itself is emptiness" means existence itself is emptiness, and emptiness itself is existence. However it takes the stand on the side of the latter, "emptiness itself is existence," to enter the Way.
The second view is the door of non-reality, and claims that the theory of "existence itself is emptiness," contrary to the first door, is the true way to enter the Way.
The third view is the intermediate middle ground of accepting both existence and non-existence or emptiness to examine the both doors to enter the Way.
The fourth view is the negation of both existence and non-existence or emptiness, contrary to the third view, to enter the Way, both being unattainable.