
Belief is integral to behavior. In cultures, both ancient and modern, religious belief and superstition shape cultural mores, laws, assumptions, and attitudes. This is why, in one culture, suicide is considered the greatest of crimes. While in another culture it is considered to be an honorable end to one’s life. Our beliefs shape the way we live, interact with others, and see the world. Just as this is true for us, it should be true for the peoples, characters, and races in the worlds we create.
The easiest, and most common, way of doing this is to pattern the beliefs of your fantasy world off of your own beliefs. This is why much of modern fantasy holds to a Judeo-Christian ethic. Even those western authors who are openly hostile towards Christianity see suicide, stealing, and murder as bad things. They see monogamy as proper and polygamy as unnatural. They value honesty, courage, independence, and freedom. These values and beliefs infect their writing.
Do not mistake my meaning. I use the word infect not because of its often negative associations but because it is the most apt terminology. I could say that these beliefs permeate our writing, and it would be true, but it would not encompass the full scope of the event. These beliefs inevitably make their way into our writing, sometimes intentionally, but often without our awareness. This is neither bad nor good of itself; it simply is. Like a bacteria that enters the body unknown and takes up habitation, our own beliefs enter the worlds and stories we create. Like a bacteria these beliefs can be beneficial or detrimental depending on their nature, and the nature of their surroundings within the story. It is easy, often unconsciously so, to write a world that corresponds with the author’s view of the world. On the other hand if one is trying to create a specific culture that does not conform to his/her view of the world then that author must be careful not to write his/her own beliefs into that culture.
Robert Howard’s Conan the Barbarian is an excellent example of a well written cultural shift. Through the short stories about Conan we see the man’s own cultural beliefs and standards conflict with the world around him. That which Conan values is often scorned by others. That which Conan finds scornful is often valued. Howard’s character brings to life the conflict that differing cultural mores create. In fact it is one of the primary themes of the Conan stories.

To create such an alien culture the author must begin with the most basic beliefs and values of that culture. For example, in my own world of Avnul, there is a race known as the Saru. The Saru are a reptilian race with an extremely high birth rate, each female will lay a clutch of between one hundred and five hundred eggs yearly. They also are possessed of the firm belief that they are trapped in a never-ending cycle of lives and that their only rest is found in the short period of death between these lives.
Because of this, and of the basic needs of any race, a great deal of religious law and superstition has grown up around the event of death. The Saru have developed a very strict caste system and how well you live within your caste will determine what caste you are in your next life. Furthermore, because death is viewed with such reverence, and desire, by the majority of the populace a very complex set of rules has developed to determine how, and when, it is appropriate to die. If a Saru does not die properly then that Saru becomes a wandering spirit, unable to rest between this life and the next.
When a child dies it also becomes a wandering spirit, because it is wickedness to die before having a chance to contribute to the community. Thus, children who die are assumed to have been wicked in their previous life, this allows the community to understand why the child would be allowed to die and forced to wander between lives. The Saru have developed a long list of ways to die well, and ways to die poorly.
Also, because of this emphasis on death murderers are seen as heroes. They risk the wrath of the gods (and thus their own chance to rest) in order to send others to their rest. Healers, on the other hand, are seen as villains because (illness or sincere injury being a proper way to die) they force the dying away from their rest and back into the horrors of life.

Among the Saru cannibalism is considered the greatest of all possible crimes. This is because the Saru believe that, for one to rest between lives, the body must be buried in a river. Those that die poorly are buried in the earth, which leads their souls to wander. Those that die well are placed into Kumrii (the Saru god of death and rebirth that lives in all rivers), which allows their souls to rest. If a Saru is consumed then the soul cannot rest.
There is much more to say about their beliefs, but you can see that the Saru’s basic beliefs about death drastically affect their culture and interactions among one another and with other cultures. Their basic beliefs shape the entirety of their culture. These issues of culture and belief are very important for us, as authors and world-builders, to pay attention to. They can be the difference between a believable world, and an unbelievable one. Or the difference between a good story, and a great one.