He refined the philosophy of 'Yugen' (the subtle and profound), a concept proposed by Toshinari (his father), advocated the philosophy of 'Ushin' (sentiment with artistic sensibility), and wielded enormous influence over the poetry of the ensuing generations.
俊成の「幽玄」をさらに深化させて「有心（うしん）」をとなえ、後世の歌に極めて大きな影響を残した。