大般涅槃經義記 6.53

6.53

Next, it turns back to extensively explain the second gate, nature and marks: "Furthermore, the bodhisattva both sees and knows" summarizes and introduces it. Below, it distinguishes them: permanence, impermanence, and so forth are conventional truth; the marks of dharmas are coarse and apparent, easy to discern and understand, and knowing them clearly is therefore called seeing. Impermanence, suffering, and so forth are dharmas of birth and death; permanence, bliss, self, and so forth are the dharmas of the Buddha's nirvāṇa of expedient means; the Tathāgata's dharmakāya and sentient beings' buddha-nature are profound, subtle, and difficult to fathom; knowing them is difficult to make clear, so it is not called seeing, but merely spoken of as knowing. Therein, it first clarifies knowing the Buddha's dharmakāya, and afterwards clarifies knowing the nature.