俱舍論頌疏論本 2.104

2.104

The explanation says: 'The five external are cognized by two': the five objects, form and the like, are called the five external [elements]. These five external objects are cognized by two consciousnesses: first, they are cognized by the five consciousnesses; second, they are cognized by the mental consciousness. Excluding these five elements, the remaining thirteen elements should be understood by implication to be cognized solely by the mental consciousness, because they are not objects of the collection of the five consciousnesses.