ak ening ▁in ▁order ▁to ▁end ▁suffering . ▁Some ▁contemporary ▁Ther av adin ▁figures ▁have ▁thus ▁indicated ▁a ▁sympath etic ▁st ance ▁toward ▁the ▁Mah ay ana ▁philosophy ▁found ▁in ▁the ▁Heart ▁S ut ra ▁and ▁the ▁M ū lam ad hy am ak ak ā rik ā . ▁ ▁The ▁Mah ay an ists ▁were ▁bother ed ▁by ▁the ▁substantial ist ▁thought ▁of ▁the ▁Sar v ā st iv ā d ins ▁and ▁S aut r ā nt ik ins , ▁and ▁in ▁emphas izing ▁the ▁doctrine ▁of ▁ś ū ny at ā , ▁David ▁Kal up ah ana ▁holds ▁that ▁they ▁endeav ored ▁to ▁preserve ▁the ▁early ▁teaching . ▁The ▁Ther av ad ins ▁too ▁ref uted ▁the ▁Sar v ā st iv ā d ins ▁and ▁S aut r ā nt ik ins ▁( and ▁follow ers ▁of ▁other ▁schools ) ▁on ▁the ▁grounds ▁that ▁their ▁theories ▁were ▁in ▁conflict ▁with ▁the ▁non - subst ant ial ism ▁of ▁the ▁canon . ▁The ▁Ther av ada ▁arguments ▁are ▁preserved ▁in ▁the ▁Kath av at th u . ▁ ▁Op in ions ▁of ▁sch ol ars ▁Some ▁western ▁sch ol ars ▁still ▁regard ▁the ▁Ther av ada ▁school ▁to ▁be ▁one ▁of ▁the ▁Hin ay ana ▁schools ▁referred ▁to ▁in ▁Mah ay ana ▁literature , ▁or ▁regard ▁Hin ay ana ▁as ▁a ▁syn onym ▁for ▁Ther av ada , ▁although ▁there ▁is ▁strong ▁evidence ▁that ▁the ▁Ther av ada ▁schools ▁were ▁in ▁existence ▁as ▁is , ▁long ▁before ▁Mah ay ana