Wonhyo is well known not only as a scholar but also as an exemplary model of his public relief activities. This paper is an attempt to find the theoretical basis of his altruism in his academic writings. For this purpose, taking the theory of postponement of nirvāṇa of a bodhisattva, which is a model of altruism widely seen in the Mahāyāna Buddhism, especially in the East Asian tradition, as a clue, I examined the tension between the postponement of nirvāṇa and apratiṣṭhita-nirvāṇa, the ultimate model of altruism in Mahāyāna Buddhism, and examined how Wonhyo solved the problem. The postponement of nirvāṇa, which seems to have originated from the scriptures of the Pure Land Buddhism, is based on the traditional view of nirvāṇa that altruistic acts are impossible when entering nirupadhiśeṣa-nirvāṇa. In contrast, prakṛti-nirvāṇa and apratiṣṭhita-nirvāṇa are Mahāyānic versions of nirvāṇa based on the śūnyatā thought of the Prajñāpāramitā literature. In particular, apratiṣṭhita-nirvāṇa is a reinterpretation of the traditional sopadhiśeṣa-nirvāṇa from the point of view of Mahāyāna, and it is a groundbreaking idea that considers the altruistic acts itself as nirvāṇa while repeating reincarnations. As the Mahāyānic view of nirvāṇa is established, the postponement of nirvāṇa loses its influence in the Indian Buddhist tradition. Wonhyo seems to have deeply understood the concepts of postponement of nirvāṇa, prakṛti-nirvāṇa, and apratiṣṭhita-nirvāṇa, and commented on Mahāparinirvāṇa-sūtra, freely quoting the scriptures in which these concepts appeared. However, Wonhyo does not seem to recognize the tension between the postponement of nirvāṇa and apratiṣṭhita-nirvāṇa. The reason is, first of all, that the Mahāparinirvāṇa-sūtra he comments on does not deal with this issue. Therefore, Wonhyo would not have had to deal with problems that did not appear in the scriptures. Next, it may be because he came across the scriptures at the stage where the tension between apratiṣṭhita-nirvāṇa and postponement of nirvāṇa was resolved due to the establishment of the concept of apratiṣṭhita-nirvāṇa. The postponement of nirvāṇa appears in Vimalakīrti-nirdeśa and Laṅkāvātara-sūtra, which he cites, but it is already reinterpreted by prakṛti-nirvāṇa or apratiṣṭhita-nirvāṇa. Therefore, he has no reason to comment on the opposition between postponement of nirvāṇa and apratiṣṭhita-nirvāṇa. Lastly, it is because Wonhyo creatively resolves the tension between postponement of nirvāṇa and apratiṣṭhita-nirvāṇa. Thatt is to understand the postponement of nirvāṇa as a mode of activity of sāṃbhogika-kāya and nairmāṇika-kāya by combining nirvāṇa as tathatā and the theory of kāya-traya of Buddhas. This can be evaluated as Wonhyo's original contribution as an explanatory method that does not appear in Indian Buddhist literature.
