Christianity
Among the three great monotheistic religions, Christianity has a place apart because of the trinitarian creed of this religion in its classic forms, in contradistinction to the unitarian creed of Judaism and Islam. The Christian Bible, including the New Testament, has no trinitarian statements or speculations concerning the doctrine of the Trinity—only triadic liturgical formulas invoking God the Father, Son, and Holy Spirit. It is true that Christianity also has had its Unitarians, such as the 16th-century Italian theologian Faustus Socinus, but this religion in its three classic forms of Roman Catholicism, Eastern Orthodoxy, and Protestantism acknowledges one God in three Persons: God the Father, God the Son, and God the Holy Spirit. According to Christian theology, this acknowledgment is a recognition not of three gods but that these three persons are essentially one, or as the dogmatic formulation, coined by the early Church Father Tertullian (c. 160–after 220), has it: three Persons and one substance. This conception was not accepted without contradiction, as is proved by theological disputes of the 3rd and 4th centuries. It is evident that trinitarian speculation greatly resembles the way of thinking of pluriform monotheism. It is, of course, unlikely that there are any historical connections between these phenomena; both, however, try to solve what is more or less the same problem in more or less the same manner. The main distinction is that Christianity, as a monotheistic religion, restricts itself to three Persons, whereas primitive religions have no reason to restrict the number of possible forms of the one divine substance. Like other religions that cover a large territory and have a long history, Christianity appears in a multitude of variations: there is Christian pantheism, Deism, and even, paradoxically, Christian atheism, as exemplified in the mid-20th-century “death of God” theologies.