肇論新疏 2.375

2.375

何則（徵）？言其非有者，言其非是有，非謂是非有。言其非無者，言其非是無，非謂是非無。非有非非有，非無非非無。

Why so? To say it is not existent means it is not [an entity of] existence, not that it is non-existence. To say it is not non-existent means it is not [an entity of] non-existence, not that it is non-non-existence. It is not existent, nor is it non-existent; it is not non-existent, nor is it non-non-existent.