首楞嚴義疏注經 2.333

2.333

此見及緣皆是妄心分別故有，說何為是而更立非？若了法界一相咸是一如，即同文殊無是非相，故云亦復如是

This seeing and conditions all exist due to the discriminations of the deluded mind; what could be spoken of as "is," such that one would further establish "is not"? If one realizes that the single characteristic of the dharmadhātu is entirely the one tathatā, then just like Mañjuśrī it is devoid of the characteristics of "is" and "is not"; hence he says, "are also like this."