俱舍論疏 1.249

1.249

論「若爾實界至十八界耶」，第二問數也。若六識依他起故名之為識，即唯六識，更兼五根、六境，界唯十七。若為所依義，名一意根，即更兼五根、六境，應唯十二。「六識與意更相攝故」者，攝意從識即為十七，攝識從意即為十二。

Regarding the commentary statement from "If so, the real dhātus" up to "eighteen dhātus?": this is the second question, asking about the number. If they are called consciousness because the six consciousnesses arise dependently, then there are only six consciousnesses, and together with the five faculties and six objective domains, the dhātus would be only seventeen. If named a single mind faculty in the sense of serving as the support, then together with the five faculties and six objective domains, there should be only twelve. "Because the six consciousnesses and the mind mutually subsume each other": subsuming mind into consciousness makes seventeen; subsuming consciousness into mind makes twelve.