The religions of the world have some features in common.
The Belief in One Supreme Being
This idea was repudiated by original Jainism and by original Buddhism. But in the later developments of both systems the founder was worshipped.
Judaism believed in one supreme worshipful God, Jehovah. After the period of the Exile the Jews were consistently monotheistic.
Confucianism teaches the beliefin one Supreme Being, designated either personally as Supreme Ruler or impersonally as Heaven. But Confucianism has limited the worship of this Being to only one person in China, the emperor, and only once a year, on the night of the winter solstice, December 22. Popular Confucianism encourages the common people to worship many spirits, both nature spirits and the spirits of deceased ancestors.
Zoroastrianism sets forth one cosmic power, which is supremely worshipful, Ahura Mazda. But this being is not supremely powerful, because there has always existed an opposing cosmic power, Angra Mainyu, the spirit of evil. Furthermore, Zoroastrianism recognizes many other good spirits, subordinate to Ahura Mazda, yet deserving of worship.
Both Hinduism and Taoism believe in one supreme impersonal cosmic being, named Brahma and Tao, respectively, to be meditated upon, but not exactly to be worshipped. But in both religions the popular phases have been polytheistic, characterized by the actual worship of many deities.
A definite belief in and a worship of one supreme cosmic power by all people, can be found in only four religions: Judaism, Christianity, Islam and Sikhism. These four religions agree as to the oneness of God.
The Claim of Divine Incarnation
The idea that deity can become incarnate is found in several religions, but with various settings and applications.
In philosophic Hinduism, ever since the period of the Upanishads, every object may be regarded as a temporary manifestation or embodiment or impersonation of the impersonal, non-moral, eternal Brahma, though the high cast Brahman priests are especially venerated as such.
In popular Hinduism there are several deities, who are believed to have taken the form of men. For instance, the god Vishnu, is believed to have entered upon several incarnations; the list varies from nine to twenty-two, but always includes animals. None of these Hindu avatars are represented as morally perfect, nor are they represented as manifestations of one supreme personal cosmic deity.
In Buddhism, despite its explicitly non-theistic basis, Buddha came to be regarded as a kind of incarnation, yet even so only as one of some twenty-four incarnate Buddhas, with a twenty-fifth still to come.
In Christianity, Jesus Christ is the unique incarnation, the Word of God.
In Islam, despite its dominant doctrine of the absolute transcendence of Allah, Shi’ism broke away from Sunni’ism on the issue of imams, divine incarnations. Some subsects among the Shiites differ concerning the exact number of still other incarnations, seven or twelve, and concerning the identity of the last one.