How Did Universal Religions Change the World
Universal religions such as Judaism, Christianity, Zoroastrianism, Islam, and others mostly rose between 500 BCE and 600 CE. Over this 1000 year period, Europe, North Africa, the Middle East, Central Asia, and parts of East Asia transformed from polytheistic worshiping to believing in a single god or universal philosophy. We often think of Christianity and Islam perhaps as the dominant universal religions today, but universal philosophies had begun before these religions and through the vehicle of empires universal religions spread.
Relevance of Universal Religions and Empires
Scholars and others do suspect that Judaism may have been one of the first universal religions, where only one God was seen as existing and the religion had direct impact to all rather than a select people. However, when Judaism became universal is not clear, as evidence for its earlier worship suggest many believers likely worshiped other gods as well. During the rise of large-scale empires in Eurasia, we begin to see universal philosophies spreading such as the Greek philosophy of universal world-order (kosmos).
Perhaps the biggest impact empires facilitated is they allowed people from many different ethnic and religious background to more freely intermix. Ideas now began to be shared among many people, where even polytheistic faiths were beginning to share similar concepts. After the 6th and 5th century BCE, universal ideals became more evident and this could have been a key period in the formulation of universal ideals. By the time Alexander reaches India, even Buddhism became influenced by the rising tide of universal philosophies. Zoroastrianism became an important universal faith that shared some common ideas as other universal religions, including Christianity. With the rise of Christianity in Rome, particularly in the early 4th century CE, the Persian Sasanian Empire, Rome's great rival, began to be associated with Zoroastrianism and Christianity became Rome's supported religion. To create loyalty and obedience, empires began to increasingly support one religion rather than allow many gods and religions. Persecutions soon became common in the major universal states of Rome and the Sasanian Persians. This continued in subsequent periods when the Byzantine Empire succeeded. With the spread of universal philosophies to Buddhism, this now also allowed universal faiths to spread farther east, spanning now much of the Old World.
The immediate effect of many of the universal religions is they led to the downfall of many of the old religions that once spanned Eurasia. Gradually, either through persecution, financial incentive, coercion, or just normal belief, most polytheistic religions ceased to exist, outside of some lingering stories and traditions that often became incorporated into the new universal religions. For example, many saints' days were often days in celebration of ancient gods.
Impact of Universal Religions
The impact was more than the disappearance of the old religions. Many traditions that were associated with worship began to diminish or cease all together. For instance, observations of the planets and stars became less relevant as the positioning of the starts and planets were not important in the worship of universal faiths. Old languages such as ancient Egyptian and Akkadian finally disappeared, which led to possible loss of knowledge these ancient languages possessed. Other changes though were more related to what universal religions achieved, which is a lessening of ethnic and cultural differences prevalent before and greater cohesion between multiple social groups. Social mobility in the religious orders now occurred across ethnic lines, allowing states and empires to depend on people with the same faith rather than same ruling ethnic groups. As ethnic groups shared the same god or religious ideas, then some of the ancient cultural groups disappeared. Gradually, cultural identity in places disappeared.
Common universal religions did create conflict in places where large non-universal groups persisted. For instance, Egypt still had a substantial polytheistic population until the Byzantine Emperor Justinian closed the temples in the 6th century CE.