法界次第初門 2.132

2.132

次四諦而辯十六行者，還離四諦開為十六行也。但教門既有總、別之殊，故諦有離、合之異。欲使修觀之者取理無謬，故次於四諦之下各以四行分別，則審實之義意乃愈明通。加以行名者，行以往趣為義。修此十六觀法，能趣四實之理，故名行也。或時從理得名，即十六諦也。

The explanation of the sixteen aspects following the four noble truths is because the four noble truths are divided and opened into the sixteen aspects. Since the pedagogical gates have the distinction of general and specific, the truths likewise have the difference of being separated and combined. In order that practitioners of contemplation grasp the principle without error, they are distinguished under each of the four noble truths by four aspects, so that the meaning of 'thoroughly verified and real' becomes even clearer and more comprehensible. The name 'aspect' (ākāra / practice) is added because practice (hsing) has the meaning of proceeding toward. Cultivating these sixteen methods of contemplation can lead toward the principle of the four realities; hence they are called 'practices'. Sometimes they take their name from the principle, and are thus the sixteen truths.