兩晉之際，是中國哲學史上首次進入儒、釋、道三家交涉的時期。格義佛教盛行，受玄學影響而有六家七宗的般若學說；玄學界除了出入於 儒、道之間，老、莊之間，也逐漸注意到佛教獨特的業報輪迴觀念。佛教東來，解釋善惡報應的因果輪迴(業)說，與連帶的作為輪迴主體的靈魂、精神與有我無我的複雜問題，一直是困擾當時知識分子的二大主題。由於是外來的新觀念，不可避兔的產生了格義的問題，而玄學中王何與郭象的二種「自然」觀，乃成了理解佛教，或抗衡佛教的主要理論資糧。直到隋、唐，道家(道教) 吸收了佛教作為宗教信仰的強盛因果觀念，與佛家有複雜的所謂「偷佛因果」的關係，也從因果概念針對道法自然，自然不法道的問題重新詮釋回應；同樣的，佛家的「因果」也經歷不同的變化，對於「自然」的不同理解、批評與吸收也表現在佛經翻譯中對於無待的真如法性，淨土的描繪上。本文以「自然或因果」為題，探討玄學後期思想的主流，如何由道家的自然轉變為佛家的因果口筆者從「義兼雙域」的角度論證，不論是玄學家的自然，或佛家的因果，皆有體用、本體與現象的不同觀點；並透過「道家因果」 與「佛家自然」的對比，凸顯道、佛雙方各有其雙重自然與兩重因果。自然與因果，理本不同，所見亦殊。自然本有多義，佛家因果亦有多義，玄學與佛學的格義過程，產生了種種的爭執，後來的發展，也有不同的對立、會通、融合的階段。自然或因果，可以充分說明隋、唐以降道教因果與佛家自然的相互批評與吸收融會的理由。結論指出，東晉以降，由於因果，玄學的自然讓位於佛教；然而，隋、唐以下，也由於自然，佛教的因果不得不接受自然的洗禮。事實上，道家與佛家各有其雙重的觀點。原來，玄學家觀自然者，不必視其因果；道教在發展的過程中，吸收了因果；佛教盛言因果，也未嘗捨棄自然。然或因果 ? 這一問題不僅是東晉玄學的困惑，也是比後中國哲學思想上還要激起廣泛漣漪的問題。

　　　　　In the Eastern Jin period, the inter-relationship of the three teachings of Confucianism, Buddhism and Daoism first became a philosophical issue. While most intellectual elite paid attention to the controversies between Confucianism and Daoism, or between Laozi and Zhuangzi, the foreign, uniquely Buddhist concepts of karma and samsara gradually became topics of discussion in Pure Conversation (Qingtan). Traditional literati and Buddhist monks alike had been interpreting these foreign concepts by way of geyi (matching concepts) in reference to Chinese thought. Early Chinese Buddhist schools, finding difficulties in using this technique to interpret their newly imported concepts of reincarnation and karmic retribution, along with associated problems of soul and spirit, self and non-self, came under the influence of the Wei-Jin Xuanxue (metaphysical) movement, and followed the fundamental paradigms of being and non-being in Wang Bi's and Guo Xiang's philosophies. The uses of these paradigmatic concepts became the main theoretical means both to interpret and to resist Buddhism. By Sui and Tang times, Daoism had assimilated from Buddhism profound religious teachings about causality. Through a complex relation called poaching from Buddhist causality, it responded with doctrines focusing on the causal treatment of problems in the formulation the Dao patterns itself on spontaneity, but spontaneity does not pattern itself on the Dao. As for Buddhism, causal concepts underwent various changes and interpretations as it criticized and assimilated the idea of spontaneity; these were expressed in Buddhist translations in their portrayals of true dharma nature and the Pure Land paradise. This essay expounds on the concepts of spontaneity and causality. It explores how the mainstream of late Xuanxue metaphysical thought evolved from Daoist spontaneity into Buddhist causality. The author finds that, regardless of the affiliation with either Daoist spontaneity or Buddhist causality, both traditions can be understood from their reliance on a twofold purview, i.e., that substance (ti) and appearance (yong) are two aspects of the ultimate reality. By exploring the ideas of Daoist causality and Buddhist spontaneity, we show how Daoism and Buddhism both have this double structure. The principles of spontaneity and causality are ontologically different, and their referents varied. Their uses in Xuanxue and Buddhism in the processes of matching concepts produced many struggles leading to later developments, which had many different stages of opposition, congruence, and assimilation. From the concepts of spontaneity and causality, we can reasonably explain the later developments of Daoist causality and Buddhist spontaneity in the Tang dynasty. This paper offers explanations of why the main theme of Eastern-Jin Xuanxue was dominated by Buddhist causality rather than Daoist spontaneity; and why Buddhism, after the Sui and Tang, could not avoid its baptism by ideas of spontaneity. In the final analysis, both Daoist spontaneity and Buddhist causality can be understood from a twofold purview, i.e., that substance (ti) and appearance (yong) are the two aspects of ultimate reality. Originally, practitioners of Xuanxue spontaneity had no need to pay attention to causality; but in the development of Daoism, it assimilated causality. Buddhists spoke plenty about causality yet never entirely rejected spontaneity. Spontaneity or causality? It is not only a puzzling problem in Eastern-Jin Xuanxue, but also a vexed question in Chinese philosophy since.