法華玄論 2.21

2.21

第五明雙治。初段明一乘，異昔三乘，故以三為病、一為藥，以一斥三。後章明今常，異昔無常，常為藥、無常為病，以常斥無常，故有今昔藥病相治也。若後段猶明無常者，但有前治、無後治也，則前病得消、後痾不遣也。

The fifth is clarifying the dual remedies. The first section clarifies the one vehicle, which is different from the former three vehicles; thus, the three are the illness and the one is the medicine, using the one to repudiate the three. The latter chapter clarifies present permanence, which is different from former impermanence; permanence is the medicine and impermanence is the illness, using permanence to repudiate impermanence; thus, there is mutual remedying of illness by medicine, present and former. If the latter section still clarified impermanence, there would only be the former remedy and no latter remedy; then the former illness could be dispelled, but the latter affliction could not be eliminated.