本文是探討智旭《周易禪解》解經的體例，即所謂的「四悉檀」及其釋義。智旭是把《周易》的經傳結構，卦形、卦辭、爻辭、《十翼》分別配置於「四悉檀」，再用「眾生法」、「佛法」，「觀心法」來加以闡述。本篇先藉由「四悉檀」上溯其淵源，由龍樹《中論》「四句」的兩型之思想分析，我們可以看到中土佛教對法性空義的吸收和轉化，而天臺宗就是用「心」去攝納了因緣所生法的法性空義，天臺宗也依此而建立了「中道佛性」之思想，並藉著詮釋自宗的根本經典《妙法蓮華經》，創立了釋經的模式。由南岳慧思之「眾生法」、「佛法」、「心法」到智顗的「因緣」（四悉檀）、「約教」、「本跡」、「觀心」之「天臺四釋」，最稱完備。私淑天臺的智旭綜合了南岳三法與智顗四釋，形成了自己的解經模式。智旭除了用來解佛典外，更以之解外典《周易》。智旭撰《周易禪解》之意，本為誘儒入佛，但其實智旭判教的思想很濃。儒佛雖然可以同源於真如本體，但儒雖具性德卻無修德，這亦就是智旭《周易禪解》會通《易》佛的用意，要以此開決儒典，指出向上一路。

This paper probes into the style of exegesis of Buddhist scriptures in Zhi-xu’s Zen Interpretation of Zhouyi: i.e., the so-called “four Siddhanta” and their definitions. Zhi-xu allotted Zhouyi’s structure (body of hexagram, explanation of hexagram, explanation of horizontal line and Ten Wings) to each of four Siddhanta, and further, used dharma of all living beings, Buddha-dharma and dharma of observing mind to expound it. First, this paper traces back to its source by four Siddhanta and then analyses thoughts by two types of “catuskoti” in Nagarjuna’s The Fundamentals of the Middle Way (Mulamadhyamaka-Karika). From that, we can realize Chinese Buddhism absorbed and transformed emptiness of dharma nature and the Tiantai School used “mind” to adopt emptiness of dharma nature issued from causes and conditions. According to this, the Tiantai School also produced the thought of “Buddha-nature of Middle Way”, and established a model for exegesis of Buddhist scriptures by interpreting Lotus Sutra, their own school’s fundamental scripture. It is the most comprehensive from Nanyue Hui-si’s dharma of all living beings, Buddha-dharma and dharma of mind to Zhi-yi’s four exegeses of Tiantai: i.e., causes and conditions(four Siddhanta), according to the teachings, original and traces and observing the mind. Zhi-xu, a disciple who never took lessons directly under Tiantai, integrated three Nanyue dharmas with Zhi-yi’s four exegeses to form his own model of exegesis of Buddhist scriptures. He interpreted not only Buddhist scriptures but also Zhouyi with it. His original intent in writing Zen Interpretation of Zhouyi was to lead Confucianism into Buddhism, but in fact, his thinking on classification of Buddha’s teaching is very strong. Confucianism and Buddhism have a common origin of Tathatā (true thusness or suchness). While Confucianism has virtue but no cultivating virtue, this is also a motive for integrating Yijing and Buddhism in Zhi-xu’s Zen Interpretation of Zhouyi: to carry out Confucian classics with it, and pointed out a way to get upgraded.