Essence-Function (體用) is a key concept is Southeast Asian Buddhism and particularly that of Korean Buddhism. Awakening of Mahayana Faith, attributed to Aśvaghoṣa (?80-?150 CE), employs Essence-Function. Essence-Function forms a fundamental syncretic and ecumenical application in the philosophy of Wonhyo (617–686CE). Chinul (1158 – 1210CE) and Kihwa (1376 - 1433CE) also employ and develop this idea of Essence-Function in their writings in particular ways. Woncheuk (613–696) employed the conceptual and analytical tool, Essence-Function, as an exegetical, hermeneutical and syncretic device.