首楞嚴義疏注經 5.269

5.269

以修空觀了心空寂，一切依正、自他、染淨乃至十方由心變者悉皆成空。自行既爾，亦令他人證得空性。此一向空未能具法，故云但空。

Through practicing the contemplation of emptiness, one realizes that the mind is empty and tranquil, so that all circumstantial and direct retributions, self and other, defilement and purity, and even the ten directions that are transformed by the mind, all become empty. One's own practice having become thus, one also causes others to realize the nature of emptiness. Since this one-sided emptiness is not yet able to embrace all dharmas, it is called 'mere emptiness'.