維摩經玄疏 6.25

6.25

答曰：具有二意。有故，是不空者，智慧性故，非空也。無故，說不空者，真諦法性之理即是空，此空畢竟不可得故，故言不空。言不空者，即是非真諦法性之空也，故《大智論》云：「空有二種，一者，但空；二者，不可得空。」聲聞唯得但空，智慧猶如螢光；菩薩得但空、得不可得空，智慧猶如日光。二乘同得但空，故名為同；菩薩得不可得空，名為異也。譬如掘土，除土至泥，除泥若圓，至水也。

Answer: It fully possesses both meanings. As for being non-empty because it is existent: because it is the nature of wisdom, it is not empty. As for being called non-empty because of non-existence: the principle of the dharma-nature of ultimate truth is precisely empty, and because this emptiness is ultimately ungraspable, it is called non-empty. Saying 'non-empty' means that it is not the emptiness of the dharma-nature of the ultimate truth. Therefore, the Mahāprajñāpāramitopadeśa says: 'Emptiness has two kinds: first, mere emptiness; second, ungraspable emptiness.' The śrāvaka attains only mere emptiness, whose wisdom is like the light of a firefly; the bodhisattva attains mere emptiness and attains ungraspable emptiness, whose wisdom is like the light of the sun. The two vehicles alike attain mere emptiness, hence it is called 'similarity'; the bodhisattva attains ungraspable emptiness, which is called 'difference.' It is like digging earth: removing the earth, one reaches mud; if removing the mud is complete, one reaches water.