Despite its new role as a tool for conquest, the underlying philosophical impact of religion was still largely unaddressed by the Civilization series. William Westwater, designer of the Call to Power games, describes religion as "more of a philosophical element. It might compare to a social value. For example, take the cultural philosophy of 'slavery' as represented in human history. At different times, society says it's either okay or not okay to enslave other people, embodied by cultural values which shift as a society develops. That is, religion touches on a civilization's philosophical underpinnings rather than just representing a governmental choice." The main challenge for the Call to Power development team was to find a way to reconcile player expectations about history with the ability to influence the outcome of the game. Westwater goes on to say that "It's hard trying to use historical religions, because the moment you deviate from history, you quickly get into speculation about how those religious values might interact with modern technologies. What could a society with those religious values have done with some discovery at another time? What if China was still based around Confucianism, and had not had a revolution and still had an emperor, how do you represent that scenario?" The Civilization games are really about the core tension between historical expectations and the ability for the player to reshape that history. While religion could now be used to influence the map more directly through specialized units and government choices, the underlying social and philosophical implications were still left to the player's imagination.
Civilization III added complexity in some areas while simplifying others. As Caudill explains, "Our focus is to make great games that provide players with fun and interesting choices and experiences. We don't want to be in the business of trying to make political or social statements." Fundamentalist governments were removed, and religion was absorbed into the broad concept of culture, simultaneously integral to a society's beliefs and yet still as abstract as before. "There is no doubt that religion and spirituality have been defining forces in the creation of civilization and society, but it wasn't until Civ III that we actually started to track the spread of cultural influence, and it wasn't until Civ IV that we decided to add the founding and growth of religions as a game-play mechanic." Civilization IV marked a significant redesign of the series. While the core premise remained the same, almost every aspect of the gameplay was altered. Soren Johnson, designer of Civilization IV, notes that "developing a fourth game in a series about a single topic - world history, in this case - is tough because what can we add to make the new version compelling without delving into obscure corners of subject matter unfamiliar to most players. Picking a 'big topic' let us avoid this problem as everyone has at least a passing familiarity with world religions." Fixed government types were replaced with a set of mix-and-match civic choices, including an entire category devoted to religious doctrine. Each of the religious civic options had distinct benefits and subtle drawbacks, allowing players to custom tailor their societies based on philosophical preference.