I show that in every other occurrence of this passage in Sanskrit and Chinese versions of these texts, Prajnāpāramitā is referred to as a superlative kind of practical knowledge or incantation (vidyā) and there is no mention of a mantra . Nor would we expect one, since these texts predate the assimilation of mantra into Buddhism. This suggests that mantra in the Sanskrit Heart Sutra is a mistranslation of a Chinese rendering of vidyā.

Unfortunately, as we go back in time our sources become fewer and less complete. It may be that the very idea of an ur-text is meaningless under these circumstances. All we can really do is establish the text at certain points in space and time and relate it to the appropriate historical circumstances.