Religion, with its complex social, philosophical, and political ramifications is inextricably connected to the development of human society. It's no wonder then, that the aptly named Civilization series incorporates religion and spirituality directly into the gameplay. At the same time, a game of Civilization is not meant to be a faithful model of human history, and so using the concept of religion is a bit of a gamble. After all, how can something so directly connected to actual human history be represented in a game about changing the course of society?
"Sid's games always have several defining themes with the two most important ones being that the game is truly epic feeling and that the player gets the chance to be something awesome," notes Barry Caudill, a long-time Civilization producer. "Civilization epitomizes this because the player is the ruler of an entire civilization and the scope is all of human history from 4000 BC to the near future." However, trying to implement the entirety of human development is a rather daunting task, both from a technological and design standpoint. "Of course, the computers weren't that powerful back when he made the original Civilization, so much of the 'epic-ness' had to happen in the player's imagination." The choice to simplify broad concepts was intentionally reflected in the design philosophy of the first game. "It's very intuitive that having food will make my population grow or that getting lumber from the forest will allow us to build things. Having these relatively simple and easy to understand systems allow players from almost any background to jump in and play." Even so, religion was a special case. "Topics like religion can conjure up many different experiences and expectations from various players and that makes the rules much harder for people to understand." As a result, the impact of religion in the first game was limited to placating an increasingly riotous population. "The early versions have religion as an abstraction, with Temples and Cathedrals adding to [the] overall happiness of the population, but the rest is left to the player's mind," says Caudill. "Sid accomplished the epic scope in the early games by abstracting certain things that the player's mind could fill in and having more concrete concepts drive the play." When it came to religion, a more concrete implementation would have to wait for future games.
Civilization II was a massive expansion on the series' original concept, adding more technologies, more units, and a new combat system. As the gameplay became more complex, so too did the role of religion. Caudill confirms that "with the significance of religion and spirituality in history, it was simply a matter of time before it ended up as a gameplay element." Early in-game religious elements like the Ceremonial Burial technology and Temple structure were retained, but the generic mid-game technology of Religion was replaced by the more gradual development of Polytheism, Monotheism, and Theocracy. More importantly, the Fundamentalism government type was added, which granted civilization-wide bonuses to population happiness and penalties to scientific discovery. It also enabled the Fanatic unit, allowing players to project military power onto the world map. Where religion had previously been an abstract way to reduce domestic unrest in the earlier games, it was now a concrete tool that players could wield to gain an advantage over rival civilizations. The ability for the player to use religion as an instrument for conquest was further expanded in the Call to Power games, a spin off of the Civilization core series, with the Cleric and Televangelist units. Through unconventional warfare, a player was now able to directly proselytize within cities, conferring economic bonuses that could be used to strengthen the player's position.