Wonhyo worked at a moment when Chinese Buddhism was fragmenting into schools, each with a scripture it held supreme and a technical vocabulary of its own. Silla received all of it more or less at once, without the sequence of arrivals that had made the Chinese sense of development possible, and Wonhyo's response was to ask what a doctrinal dispute actually is.
His answer, hwajaeng, is usually translated as the harmonisation of doctrinal disputes. It is not a plea for tolerance. The method assumes that a position held seriously by serious people is answering to something real, and that disagreement usually arises because two parties are affirming and denying with respect to different aspects of the same matter. The task is to find the standpoint from which the affirmation and the denial can both be granted their proper scope, and the failure being corrected is not error but partiality. He applied this to the arguments over emptiness and consciousness, over sudden and gradual attainment, and over the status of the buddha nature.
The instrument he used most was the Awakening of Faith in the Mahayana, a short text whose Indian origin is now doubted and which proposes that the mind has two aspects, suchness and arising and ceasing, neither reducible to the other. That structure gave him exactly what hwajaeng required: a single thing describable in two incompatible registers without contradiction. His commentary on it became the standard reading across East Asia, and Chinese authors cited it under the name of the commentary from east of the sea.