▁the ▁American ▁Academy ▁of ▁the ▁Art ▁and ▁Sciences , ▁in ▁ 1 9 6 9 , ▁asked ▁Par s ons ▁to ▁undert ake ▁a ▁mon ographic ▁study ▁of ▁the ▁American ▁university ▁system . ▁The ▁work ▁on ▁the ▁book ▁went ▁on ▁for ▁years ▁until ▁it ▁was ▁finished ▁in ▁June ▁ 1 9 7 2 . ▁ ▁From ▁a ▁theoretical ▁point ▁of ▁view , ▁the ▁book ▁had ▁several ▁functions . ▁It ▁subst anti ated ▁Par s ons ' ▁concept ▁of ▁the ▁educational ▁revolution , ▁a ▁cru cial ▁component ▁in ▁his ▁theory ▁of ▁the ▁rise ▁of ▁the ▁modern ▁world . ▁What ▁was ▁equally ▁intellect ually ▁comp elling , ▁however , ▁was ▁Par s ons ' ▁discussion ▁of ▁" the ▁cogn itive ▁complex ", ▁aim ed ▁at ▁explaining ▁how ▁cogn itive ▁rational ity ▁and ▁learning ▁operated ▁as ▁an ▁inter pen etr ative ▁zone ▁on ▁the ▁level ▁of ▁the ▁general ▁action - system ▁in ▁society . ▁In ▁ret ros pect , ▁the ▁categories ▁of ▁the ▁cogn itive ▁complex ▁are ▁a ▁theoretical ▁foundation ▁to ▁understand ▁what ▁has ▁been ▁called ▁the ▁modern ▁knowledge - based ▁society . ▁ ▁Ret irement ▁He ▁officially ▁retired ▁from ▁Harvard ▁in ▁ 1 9 7 3 ▁but ▁continued ▁his ▁writing , ▁teaching , ▁and ▁other ▁activities ▁in ▁the ▁same ▁rapid ▁pace ▁as ▁before . ▁Par s ons ▁also ▁continued ▁his ▁extensive ▁correspond ence ▁with ▁a ▁wide ▁group ▁of ▁colle agues ▁and ▁intellect uals . ▁He ▁taught ▁at ▁the ▁University ▁of ▁Pennsylvania , ▁Brown ▁University , ▁R ut gers ▁University , ▁the ▁University ▁of ▁Chicago ,