gregkavarnos wrote:And let's not forget the Heart Sutra.
It is tantra.
Is it or isn't it? Only a high Bodhisattva can tell for sure (riffing off an old Clarol commercial).
Lopez essentially wrote a book discussing this, his excellent Heart Sutra book. From the perspective of literary criticism the Heart Sutra can be viewed as an intermediate text between sutras and tantras.
But then how should we classify the numerous dharani texts? Probably as texts developed there is not that great a leap from dharani texts to tantra in terms of outward form.
However many tantras look outwardly like books of magic and the Heart Sutra, while being really magical, doesn't have this characteristic.