摩訶止觀 6.181

6.181

復次，體達智障無明，無自、他性、共、無因性，畢竟不可得。如持戒比丘觀無蟲水，此中動者，蟲耶？塵耶？蟲即生相，塵無生相。諦觀不已，雖知是塵，亦不明了。若謂無明有四性，性是生動；若無四性，無性無生動。雖知不動，亦不決定；雖不決定，而決定觀常住不動。前生死、涅槃二邊流動，上兩觀已止；唯有無明迴轉未息。今達心本源，無明寂靜，名「止息止」；安心此理，名「停止止」；常住之理非止非不止，對無常動故言為止，即是非止非不止，是名「中止」。具三義也。

Furthermore, one thoroughly penetrates that the avidyā that is the obstruction of wisdom has no nature of self, nature of other, nature of both together, or causeless nature, being ultimately unobtainable. It is like a precept-holding monk observing water free of insects: is that which moves within it an insect, or dust? An insect is the mark of life; dust lacks the mark of life. Observing carefully without ceasing, although he knows it to be dust, it is still not clearly distinct. If one claims that avidyā has the four natures, nature is living movement; if it lacks the four natures, having no nature, there is no living movement. Although knowing it is unmoving, one is also not yet certain; although not yet certain, one definitely contemplates it as permanently abiding and unmoving. The previous movements of the two extremes of saṃsāra and nirvāṇa have already ceased through the previous two contemplations; only the turning of avidyā has not yet ceased. Now penetrating the original source of the mind, avidyā is quiescent, which is called 'calming by cessation'; pacifying the mind in this principle is called 'calming by abiding'; the principle of permanent abiding is neither calming nor non-calming, yet contrasted with the movement of impermanence it is said to be calming, which is precisely neither calming nor non-calming; this is called 'middle calming'. It is endowed with three meanings.