翻譯名義集 6.42

6.42

【馱都】此云界。《百法疏》云：「界是因義。中間六識，藉六根發。六境牽生，與識為因，故名為界。」《法界次第》云：「界以界別為義。此十八法，各有別體，義無渾濫，故名十八界。若根相對，即有識生。識以識別為義，識依於根，能別於塵，故通名識。由此根、塵、識三，各有六法，成十八界。」此三科法，如《俱舍》云：「聚生門種族，是蘊處界義，愚根樂有三，故說蘊處界。」釋曰：「愚三者，一、愚心，為說五陰，則開心為四，合色為一。二、愚色，為說十二處，則開色為十處半，謂五根、五塵及法塵少分；合心為一處半，謂意根及法塵少分。三、愚心及色，為說十八界，則更開心為七界半，謂六識、意根、法塵少分。」皆言愚者，迷也。根三，謂上、中、下根，樂三，謂略、中、廣。如次配三科法。

[Dhātu]
Here translated as "realm" (界, dhātu). The Baifa shu says: "'Realm' has the meaning of 'cause'. The six intermediate consciousnesses are produced in reliance upon the six sense faculties. The six sense fields induce their arising and serve as causes for the consciousnesses; therefore they are called 'realms'." The Fajie cidi says: "'Realm' takes 'distinction' (界別) as its meaning. These eighteen phenomena each have their distinct essence without confusion; hence they are named the 'eighteen realms'. When faculties and objects face one another, consciousness is produced. Consciousness takes 'discernment' (識別) as its meaning. Relying on the faculties, consciousness can discern the dust-like sense fields; thus they are collectively named consciousnesses. Because these three—faculties, dust-fields, and consciousnesses—each comprise six phenomena, they form the eighteen realms."
These three categories of phenomena are as stated in the Kośa: "Accumulation, gates of arising, and lineage / Are the meanings of aggregates, bases, and realms; / Because deluded views, faculties, and inclinations are threefold, / The aggregates, bases, and realms are taught accordingly." The commentary explains: "The three types of delusion are: first, delusion regarding mind, for which the five aggregates are taught, unfolding the mind into four and combining form into one; second, delusion regarding form, for which the twelve bases are taught, unfolding form into ten and a half bases—namely the five faculties, the five fields, and a subtle fraction of the mental-object field—and combining mind into one and a half bases, namely the mental faculty and a subtle fraction of the mental-object field; third, delusion regarding both mind and form, for which the eighteen realms are taught, further unfolding mind into seven and a half realms—namely the six consciousnesses, the mental faculty, and a subtle fraction of the mental-object field." 'Delusion' in all these cases means confusion. The three faculties refer to superior, middling, and inferior faculties. The three inclinations refer to brief, middling, and extensive [expositions]. They correspond in turn to the three categories of phenomena.