請觀音經疏闡義鈔 1.83

1.83

「觀因緣」下，標藏智。「觀因緣空」標通智。「二諦觀」者，假是虛妄俗諦，空是審實真諦。今欲去俗歸真，故言觀。因緣空假是入空之詮，先須觀假知假虛妄而得會真，故言二諦觀。

From "contemplating causes and conditions" downward marks the wisdom of the Piṭaka. "Contemplating the emptiness of causes and conditions" marks the wisdom of the shared. "Contemplation of the two truths": The conventional is the false and deceptive conventional truth; the empty is the verified and real ultimate truth. Now, wishing to leave the conventional and return to the ultimate, it is called contemplation. The emptiness and conventionality of causes and conditions are the means of entering emptiness; one must first contemplate the conventional and know the conventional to be false and deceptive so as to be able to merge with the ultimate, and therefore it is called the contemplation of the two truths.