▁events , ▁providing ▁an ▁interpretation ▁of ▁in compat ibil ist ▁free ▁will . ▁St em ming ▁from ▁Cart esian ▁dual ism , ▁a ▁form ulation ▁sometimes ▁called ▁interaction al ist ▁dual ism ▁suggests ▁a ▁two - way ▁interaction , ▁that ▁some ▁physical ▁events ▁cause ▁some ▁mental ▁acts ▁and ▁some ▁mental ▁acts ▁cause ▁some ▁physical ▁events . ▁One ▁modern ▁vision ▁of ▁the ▁possible ▁separation ▁of ▁mind ▁and ▁body ▁is ▁the ▁" three - world " ▁form ulation ▁of ▁Po pper . ▁Cart esian ▁dual ism ▁and ▁Po pper ' s ▁three ▁world s ▁are ▁two ▁forms ▁of ▁what ▁is ▁called ▁ep ist em ological ▁pl ural ism , ▁that ▁is ▁the ▁notion ▁that ▁different ▁ep ist em ological ▁method ologies ▁are ▁necessary ▁to ▁att ain ▁a ▁full ▁description ▁of ▁the ▁world . ▁Other ▁forms ▁of ▁ep ist em ological ▁pl ural ist ▁dual ism ▁include ▁psych oph ys ical ▁parallel ism ▁and ▁e pi phen omen al ism . ▁Ep ist em ological ▁pl ural ism ▁is ▁one ▁view ▁in ▁which ▁the ▁mind - body ▁problem ▁is ▁not ▁redu cible ▁to ▁the ▁concepts ▁of ▁the ▁natural ▁sciences . ▁ ▁A ▁contrast ing ▁approach ▁is ▁called ▁physical ism . ▁Phys ical ism ▁is ▁a ▁philosoph ical ▁theory ▁holding ▁that ▁everything ▁that ▁exists ▁is ▁no ▁more ▁extensive ▁than ▁its ▁physical ▁properties ; ▁that ▁is , ▁that ▁there ▁are ▁no ▁non - phys ical ▁subst ances ▁( for ▁example ▁phys ically ▁independent ▁minds ). ▁Phys ical ism ▁can ▁be ▁re duct ive ▁or ▁non - re duct