 Kūkai has been regarded as the first comprehensively philosophical thinker in Japanese intellectual history. The influence of Mahāyāna philosophy is noticeable but they are interpreted through the lens of Mantrayāna with its emphasis upon the inseparability of ritual practice from theoretical doctrine. Traditionally, his thought has been divided into the following aspects: 1) the theoretical (kyōsō) which explicates the uniqueness and distinction of esoteric Buddhism (mikkyō) as opposed to exoteric Buddhism (kengyō) and demonstrates its validity and efficaciousness; and 2) the practical (jisō), which prescribes his method of meditation and ritual. Ultimately however the theoretical and the practical are inseparable in Kūkai’s thought. Within the deep profundity and subtleties of his doctrine, one recognizes philosophical elements inherited from Madhyamaka, Yogācāra, T’ien-t’ai (Tiantai), and Huayen (Huayan) Buddhist thought. But with these are incorporated the elements of devotional piety and magico-esoteric practice even in his theoretical writings. What is especially pronounced and distinct in his thought is the significance of bodily experience and practice. Buddhist truths for Kūkai were not simply meant to be intellectually mused over but to be experienced through bodily practice. One might say then that for Kūkai it is the body that provides the medium whereby theory and practice, doctrine and ritual, thought and experience, are non-dualistic.