Religion is a set of cultural system coupled with a set of beliefs observed and followed by a given group of people seeking to understand self and the universe as a whole. Some religions consist of members from a small, homogeneous group of people; for example, an ethnic group, while others cut across ethnic, cultural and racial barriers. It is this latter form of religions which transcend geographical borders that qualify as universal religions. Thus, a universal religion is one, which has followers not confined to a particular geographical location but rather has adherence and followers among various people of the world, irrespective of their cultures, nationalities or race.
Major universal religions of today had their worldwide spread influenced by number of factors. Three among the universal religions – Christianity, Islam and Buddhism, spread to various part of the globe through their ‘missionaries’ or through other historical events which helped their doctrines and teachings appeal to many. The missionary mode of spreading these religions was to a greater extent a voluntary acceptance of the beliefs by new converts. The missionaries had to 'sell' their religion through teachings, which appeal to the masses. For example, Buddha missionaries will emphasis the concept of equality in their religion appealing to many of the new converts who felt oppressed by the caste system that does not recognize equality of all humans. Many of the factors were more complex that helped the wide spread of these religion.
The adapting by the political system to religion helped to strengthen and spread these religions. The Roman Empire adapted, for example, the Christian religion after realizing that its teaching was increasingly appealing to the masses even after efforts to persecute Christians (Saint Augustine, 24). Thus, Christianity became a way of life in the empire and sanctioned by the emperor. The secular government even helped build churches in major cities. It also installed Bishops in these cities and assigned them secular duties. With religion gain in support from secular government: the original beliefs and doctrines had to change to gain wide acceptance. This led to split between the conservatives and liberals. This, in turn, helped to spread the religion even further as each function tries to do out the other.
Trade and commerce were also keys to spreading of these religions. Buddhism, for example, spread with the trade merchants along the silk road of Southwest Asia who introduced it to other traders. Thus, both Buddha missionaries together with the need for trade helped Buddhism spread far and wide in Southwest and Southeast Asia. Trade had helped religion to grow and spread in other ways. Since many cities and territories needed a trade to help grow their economies, they were tolerant to different cultures and religions (Brodd, 20). This is also true with Islam where traders introduced religion to new places as they expanded their trade routes.
Conquest and forceful conversion was another factor, which helped in spreading these religions. Islam is the notable example. By conquering territories and establishing empires, which imposed Islam to the inhabitant, many of the Middle East and North African territories converted to Islam. This mode of spreading religion was thus effective in establishing Islam in many parts, since Islam allowed such a method of conquest and forceful conversion of non –Muslims. On the other hand, Christianity and Buddhism appealed to new converts by emphasizing love and humility especially among the oppressed and poor. In all the three Religions, no one factor was responsible for the widespread of each, but rather a combination of factors contributed to their spread and adaptability. However, the combination of factors differs from one religion to another.