法華義疏 6.7

6.7

此教所興正為破執三乘是實，故宜明三乘是方便，即是開方便門，然後始得顯真實義，故寄父子明三乘是方便也。所言寄索車譬顯一乘是真實者，下明等賜即是有一，將明一有宜辨三無，三無不彰則一有不顯，故寄索三以顯無三；如其有三則不索三，以其索三故知無三，在三既無一有便顯，故方得賜一也。蓋是經之正意，不須異釋也。

The arising of this teaching is specifically to shatter the attachment to the triyāna as real; therefore it is appropriate to clarify that the triyāna is an upāya, which is opening the door of expedient means, and only then can the real meaning be revealed. Thus, he relies on father and sons to clarify that the triyāna is an upāya. As for relying on the parable of requesting the carriages to reveal that the ekayāna is real: the clarification below of bestowing equally is having one. To explain that the one exists, it is appropriate to discern that the three do not exist; if the nonexistence of the three is not manifested, then the existence of the one is not revealed. Therefore, he relies on requesting three to reveal the nonexistence of three; if there were three, they would not request three; because they requested three, we know there are no three. Since the three do not exist, the existence of the one is immediately revealed, and only then can he bestow the one. This is the correct intention of the sūtra; no other explanation is needed.