Wǒnhyo interprets Buddha-nature as nature of One Mind (一心). He insists that the essence of Buddha-nature is precisely the same as essence of One Mind. The essence of One Mind is only realized by the Buddha. Hence it is explained that this Mind is Buddha-nature. Wǒnhyo himself considers Buddha-nature to be the One Mind, since the essence of One Mind leaves all extremes far off, has no corresponding place and thus corresponds to every place. The essence of One Mind transcends and embraces cause and effect. Wǒnhyo interprets Buddha-nature
as having the same meaning i.e. One Mind, in all Buddhist scriptures. His unique Hoe'tong (會通, harmonization) theory is focused on harmonizing different doctrines and sects within the same Buddhist Teaching. He combined all the different Buddhist theories into One Flavor (一味). Wǒnhyo did not reject the existing assertions on Buddha-nature but integrated them in a system elucidating the process of One Mind.
Kim, Young-suk. "Wǒnhyo's Conception of Buddha-Nature in the Thematic Essential of the Mahāparinirvāṇa-sūtra." International Journal of Buddhist Thought and Culture
2 (2003): 195–213. http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.592.7690&rep=rep1&type=pdf
.; Wǒnhyo's Conception of Buddha-Nature in the Thematic Essential of the Mahāparinirvāṇa-sūtra; Wǒnhyo's Conception of Buddha-Nature in the Thematic Essential of the Mahāparinirvāṇa-sūtra; Wǒnhyo; Mahāparinirvāṇasūtra; Young-suk Kim;