According to the theory on the origin of bushi by 'samurai function,' the social class considered as bushi was limited to shodaibu or elite cavalry warriors coming from samurai status, whose family business was military art, during the period when the Minamoto clan and the Taira clan emerged; and later, through the medieval times, the class of 'bushi in a broad sense' came to have the master-subordinate relationship with 'bushi in a narrow sense' and expanded after the Muromachi period.
「職能」起源論では、武士とみなされる社会階層は源氏、平氏などの発生期には武芸を家業とする諸大夫、侍身分のエリート騎馬戦士に限定されていたとし、その後、中世を通じて「狭義の武士」との主従関係を通じて「広義の武士」とみなされる階層が室町時代以降拡大していった。