Kukai's intention was, as he wrote in the general introduction appended to the volume of Heaven, 'the volumes are titled after the universe and because they are so everlasting as the sun and the moon are, they are collectively called hifuron (important theory).'
これについて空海は、天の巻に付された総序において「配巻軸於六合、懸不朽於兩曜、名曰秘府論。（巻軸を六合に配し、不朽を両曜に懸け、名づけて秘府論という）」とその意図を述べている。