'The Heart Sutra is named a 'mother sutra' because it deals with the topic of Prajnaparamita, which is the mother to all the Aryas.It is also called the 'mother of all the Buddhas of the three times'.It is said in the sutras, as well as in many commentaries that the attainment of Buddhahood by all the Buddhas of three times depends on this Prajnaparamita.So the importance of Prajnaparamita is explained in the different sutras and shastras by saying that only by depending on this Prajnaparamita is one able to become a Buddha.So whether it is the present Buddha, a Buddha in the past or a Buddha yet to come, this result is due only to the Prajnaparamita.This refers not only to the Arya Buddha but also the other three types of Aryas.If the attainment of Buddhahood depends on Prajnaparamita then naturally the attainment of the level of Bodhisattva depends on it as well.