妙法蓮華經玄義 2.161

2.161

As for the two truths of the perfect teaching: it directly explains the inconceivable two truths. The real is precisely the conventional; the conventional is precisely the real. It is like the wish-fulfilling jewel: the jewel is used as a metaphor for the real, and its function as a metaphor for the conventional. The jewel is the function, and the function is the jewel; non-dual yet dual, we merely distinguish the real and the conventional. With respect to this, there are also [the meanings of] according with sentiment, wisdom, and so on. Śāriputra said: 'The Buddha, with various causes, / metaphors, and skillful words, / his mind tranquil as the sea— / hearing him, the net of my doubts was severed.' Such is its meaning.