俱舍論頌疏論本 2.10

2.10

釋曰：欲界所繫具足十八。色界所繫唯十四種，除香、味境及鼻、舌識。除香、味者，段食性故，色界無段食，故無香味。除鼻、舌識，無所緣故，鼻識緣香，舌識緣味，既無香、味，故無鼻舌識。

Explanation: Those bound to the desire realm are fully eighteen. Those bound to the form realm are only fourteen, excluding the objects of smell and taste, and the consciousnesses of nose and tongue. Smell and taste are excluded because their nature is material food (kavaḍīkārāhāra); in the form realm there is no material food, and therefore no smell or taste. Nose and tongue consciousnesses are excluded because they lack cognitive objects: nose consciousness takes smell as object and tongue consciousness takes taste as object; since smell and taste are absent, nose and tongue consciousnesses are absent.