For a philosophical study of Dōgen's concept of language cf. Ralf Müller: Dōgens Sprachdenken: Historische und symboltheoretische Perspektiven [Dōgen’s language thinking: Systematic perspectives from history and the theory of symbols], Welten der Philosophie, vol. 13. Freiburg/München: Verlag Karl Alber, 2013; reviewed by Steffen Döll in Philosophy East & West Volume 65, Number 2 April 2015 636–639.