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Belief systems are one of the most important factors to societies because they form the basis for people's beliefs in how they should live, how they should interact with one another and foreign people, and how they answer questions about their purpose in life and the divine. There has never been a society or civilization in history that has never had at least one belief system, and several belief systems can be combined with others. At the founding of primary belief systems, they played a highly active role in people's lives, and were almost always religious. A person's belief system formed the "lens" or basis through which they viewed the world and decided how to act, or was at least had a significant part in people's decisions. But over time, all belief systems are forced to change due to unforeseen developments in the regions where they are practiced. Cultural diffusion as one society interacted with another also forces change in order for a belief system not to lose followers to another one that it encounters. As the ideals of a belief system adjust to fit the changing times, it combines its principles with another, takes some of the other's characteristics to keep uncertain followers, and/or becomes less demanding of the people. All of these results in the loss of influence from a belief system on the lives it lives through because of how it becomes more like others, and less firm in a person's life. The inevitable change in belief systems over time negatively affects societies because they lose a supporting foundation of their culture and its ideologies as the original ideals of the belief system become less important through cultural diffusion and the need to survive, which leads to belief systems becoming something they were never intended to be by the founders.