The motive is uncertain, but it is hard to believe that Tokinobu, who was the son of MINAMOTO no Masanobu, who was Sadaijin, and had the political power which could suppress the Sessho (regent) FUJIWARA no Kaneie at that time, and was probably due to a pessimistic view on life according to "Shui Ojo-den" and "Genko shakusho" (History of Buddhism of the Genko era).
動機は不明であるが、当時摂政藤原兼家を牽制しうる政治力を有した左大臣源雅信の子である時叙に将来性に問題があるとは考えにくく、『拾遺往生伝』・『元亨釈書』などが記す厭世観によるものとする可能性がある。