佛說盂蘭盆經疏 1.4

1.4

Intending to explain this sūtra, I first open four sections: first, the causes for which the teaching arose; second, the pitakas and vehicles by which it is subsumed; third, determining the central tenets; fourth, correctly explaining the sūtra text. In the first there are again four: first, to repay past causes; second, to respond to the present request; third, to demonstrate filial piety; fourth, to reveal the superior field.