印度中世思想的重大變化之一，乃是新神觀的開展，也就是自在天（Īśvara）的出世所帶來之重大改變。自在天當為宇宙之最高主宰，以其千變萬幻之身軀，應時而生，普度眾生，為苦難人間之終極救度者。此一神觀為印度宗教開啟了一個新的紀元，更標示著印度教之誕生。本篇論文從自在天觀念的流布來看中世印度教之興起。同時，透過自在神觀的開展來檢視印度宗教教在思想與實踐上之重大轉變。 值得一提的是，自在天思想的出現也代表著解脫方式的重大改變。信者可透過對於神的完全依賴得到救度。此一救度觀跟沙門傳統透過一己修行的自力解脫思想有著根本上的不同。信奉或信愛（Bhakti）2與密續（Tantra）思想的興起，都與此一神觀有著密切的關係。因其廣開救度之門，此一神觀逐漸成為印度宗教的主流思想，沙門的傳統解脫觀遂遭到前所未見之挑戰。

A radical transformation of the religious climate in medieval India was the unfolding of new theism, i.e. the advent of Īśvara and sweeping changes brought about thereafter. Īśvara was regarded as the highest ruler of the universe, and through his body ever-changing myriad forms, responded to the times and was born to save the multitudes of living creatures as the ultimate redeemer of human suffering. This new divine vision of god opened a new era for Indian religions and also marked the birth of Hinduism. This paper investigates the rise of Hinduism in medieval times from the perspective of the spread of Īśvara. Simultaneously, it also examines major changes in both teachings and practices of Indian religions that came about as the divine vision of Īśvara unfolded. It is worth noting that the emergence of Īśvara ideology was also representative of significant changes in methods of liberation. Devotees could attain salvation by relying completely on Īśvara. This view of salvation was fundamentally different from that of the Śramanic tradition in which liberation could only be achieved through one’s own self-cultivation efforts. The beginnings of Bhakti（faithful devotion or devotional love） and Tantra have an intimate relationship with this divine vision of Īśvara. Because this broadened the means of salvation, Īśvara gradually became part of mainstream thought in Indian religion, while the traditional Śramaṇic views of liberation subsequently encountered challenges they had never seen before.