Comparative religion is the branch of the study of religions concerned with the systematic comparison of the doctrines and practices of the world's religions. In general the comparative study of religion yields a deeper understanding of the fundamental philosophical concerns of religion such as ethics, metaphysics, and the nature and form of salvation. Studying such material is meant to give one a richer and more sophisticated understanding of human beliefs and practices regarding the sacred, numinous, spiritual, and divine.
In the field of comparative religion, a common geographical classification of the main world religions includes Middle Eastern religions (including Iranian religions), Indian religions, East Asian religions, African religions, American religions, Oceanic religions, and classical Hellenistic religions.
Social scientists in the 19th century took a strong interest in comparative and "primitive" religion through the work of Max Müller, Edward Burnett Tylor, William Robertson Smith, James George Frazer, Émile Durkheim, Max Weber, and Rudolf Otto.
The comparative study of religions is an academic discipline which has been developed within Christian theology faculties, and it has a tendency to force widely differing phenomena into a kind of strait-jacket cut to a Christian pattern. The problem is not only that other 'religions' may have little or nothing to say about questions which are of burning importance for Christianity, but that they may not even see themselves as religions in precisely the same way in which Christianity sees itself as a religion.
In the study of comparative religion, the category of Abrahamic religions consists of the three monotheistic religions, Christianity, Islam and Judaism, which claim Abraham (Hebrew Avraham ; Arabic Ibrahim ? ) as a part of their sacred history. Smaller religions such as Bahá'í Faith that fit this description are sometimes included but are often omitted.
The original belief in the One God of Abraham eventually became strictly monotheistic present-day Rabbinic Judaism. Christians believe that Christianity is the fulfillment and continuation of the Jewish Old Testament. Christians believe that Jesus (Hebrew Yeshua ) is the Messiah (Christ) foretold in the Old Testament prophecy, and believe in subsequent New Testament revelations based on the divine authority of Jesus in Christian belief (as the Incarnation of God). Islam believes the present Christian and Jewish scriptures have been corrupted over time and are no longer the original divine revelations as given to the Jewish people and to Moses, Jesus, and other prophets. For Muslims, the Qur'an is the final, complete revelation from God (Arabic ? Allah), who believe it to have been revealed to Muhammad alone, who is believed by Muslims to be the final prophet of Islam, and the Khatam an-Nabiyyin, meaning the last of the prophets ever sent by Allah ("seal of the prophets"). Based on the Muslim figure of the Mahd?, the ultimate saviour of humankind and the final Im?m of the Twelve Imams, Ali Muhammad Shirazi, later known as Bab, created the Bábí movement out of the belief that he was the gate to the Twelfth Im?m. This signalled a break with Islam and started a new religious system, Bábism. However, in the 1860s a split occurred after which the vast majority of Bábís who considered Mirza Husayn `Ali or Bahá'u'lláh to be Báb's spiritual successor founded the Bahá'í Movement, while the minority who followed Subh-i-Azal came to be called Azalis. The Bahá'í division eventually became a full-fledged religion of its own, the Bahá'í Faith. In comparison to the other Abrahamic religions, Judaism, Christianity and Islam, the number of adherents for Bahai faith and other minor Abrahamic religions are not very significant.
Out of the three major Abrahamic faiths, Christianity and Judaism are the two religions that diverge the most in theology and practice.
The historical interaction of Islam and Judaism started in the 7th century CE with the origin and spread of Islam. There are many common aspects between Islam and Judaism, and as Islam developed, it gradually became the major religion closest to Judaism. As opposed to Christianity, which originated from interaction between ancient Greek, Roman, and Hebrew cultures, Judaism is very similar to Islam in its fundamental religious outlook, structure, jurisprudence and practice. There are many traditions within Islam originating from traditions within the Hebrew Bible or from post-biblical Jewish traditions. These practices are known collectively as the Isra'iliyat.
The historical interaction between Christianity and Islam connects fundamental ideas in Christianity with similar ones in Islam. Islam accepts many aspects of Christianity as part of its faith - with some differences in interpretation - and rejects other aspects. Islam believes the Qur'an is the final revelation from God and a completion of all previous revelations, including the Bible.
Several important religions and religious movements originated in Greater Iran, that is, among speakers of various Iranian languages. They include Mithraism, Ætsæg Din, Yazdanism, Ahl-e Haqq, Zurvanism, Mandaeism, Manichaeism, and Mazdakism.
Most scholars believe that Hinduism is the oldest religion in the world., with origins perhaps as far back as to the prehistoric times, or 5000 years. So "the kinship of the religions of India stems from the fact that Jains, Buddhists and Sikhs look back to Hinduism as their common mother."
Gautama Buddha is mentioned as an Avatar of Vishnu in the Puranic texts of Hinduism. Most Hindus believe the Buddha accepted and incorporated many tenets of Hinduism in his doctrine, however, Buddhists disagree and state there was no such thing as Hinduism at the time of Buddha and in fact, "Indeed, it absorbed so many Buddhist traits that it is virtually impossible to distinguish the latter in medieval and later Hinduism." Prominent Hindu reformers such as Mahatma Gandhi and Vivekananda acknowledge Buddhist influence. Gandhi, like Hindus himself did not believe Buddha established a non-Hindu tradition. He writes, "I do not regard Jainism or Buddhism as separate from Hinduism."Zoroastrianism too is an Indian religion and its founder, Zarathushtra Spitama, was a Kashmiri Pandit born in Kashmir. Yungdrung Bon is another Indian religion and its founder, Tonpa Shenrab Miwoche, was born in Dardistan.
A Taoic religion is a religion, or religious philosophy, that focuses on the East Asian concept of Tao ("The Way"). This forms a large group of religions including Taoism, Confucianism, Jeung San Do, Shinto, I-Kuan Tao, Chondogyo, Chen Tao and Cao Dai. In large parts of East Asia, Buddhism has taken on some taoic features.
Tao can be roughly stated to be the flow of the universe, or the force behind the natural order. It is believed to be the influence that keeps the universe balanced and ordered and is associated with nature, due to a belief that nature demonstrates the Tao. The flow of Ch'i, as the essential energy of action and existence, is compared to the universal order of Tao. Following the Tao is also associated with a "proper" attitude, morality and lifestyle. This is intimately tied to the complex concept of De, or literally "virtue" or "power." De is the active expression of Tao.
Taoism and Ch'an Buddhism for centuries had a mutual influence on each other in China, Korea and Vietnam. These influences were inherited by Zen Buddhism when Ch'an Buddhism arrived in Japan and adapted as Zen Buddhism.