Shamanism is classified as animism, a worldview in which spiritual agency is assigned to all things, including natural elements such as rocks and trees. Sometimes associated with the idea of dual souls—a day soul and a night soul, the latter of which can wander in dreams—and sometimes with unnamed and disembodied spirits believed to be associated with living and nonliving things, animism was at first understood by anthropologists as a primitive step toward more complex religions. In his work Primitive Culture (1871), British anthropologist Sir Edward Tylor, considered the first academic anthropologist, identified animism as a proto-religion, an evolutionary beginning point for all religions. As population densities increased and societies developed more complex forms of social organization, religion mirrored many of these changes. With the advent of state societies, religion became institutionalized. As population densities increased and urban areas emerged, the structure and function of religion shifted into a bureaucracy, known as a state religion. State religions are formal institutions with full-time administrators (e.g., priests, pastors, rabbis, imams), a set doctrine of beliefs and regulations, and a policy of growth by seeking new practitioners through conversion. While state religions continued to exhibit characteristics of earlier forms, they were now structured as organizations with a hierarchy, including functionaries at different levels with different specializations. Religion was now administered as well as practiced. Similar to the use of mercenaries as paid soldiers in a state army, bureaucratic religions include paid positions that may not require subscribing to the belief system itself. Examples of early state religions include the pantheons of Egypt and Greece. Today, the most common state religions are Christianity, Islam, Buddhism, and Hinduism. Rather than part-time shamans, tribal and state religions are often headed by full-time religious leaders who administer higher levels within the religious bureaucracy. With institutionalization, religion began to develop formalized doctrines, or sets of specific and usually rigid principles or teachings, that would be applied through the codification of a formal system of laws. And, unlike earlier religious forms, state religions are usually defined not by birthright but by conversion. Using proselytization, a recruitment practice in which members actively seek converts to the group, state religions are powerful institutions in society. They bring diverse groups of people together and establish common value systems. There are two common arrangements between political states and state religions. In some instances, such as contemporary Iran, the religious institution and the state are one, and religious leaders head the political structure. In other societies, there is an explicit separation between religion and state. The separation has been handled differently across nation-states. In some states, the political government supports a state religion (or several) as the official religion(s). In some of these cases, the religious institution will play a role in political decision-making from local to national levels. In other state societies with a separation between religion and state, religious institutions will receive favors, such as subsidies, from state governments. This may include tax or military exemptions and privileged access to resources. It is this latter arrangement that we see in the United States, where institutions such as the Department of Defense and the IRS keep lists of officially recognized religions with political and tax-exempt status. Among the approximately 200 sovereign nation-states worldwide, there are many variations in the relationship between state and religion, including societies that have political religions, where the state or state rulers are considered divine and holy. In North Korea today, people practice an official policy of juche, which means self-reliance and independence. A highly nationalist policy, it has religious overtones, including reverence and obeisance to the state leader (Kim Jong Un) and unquestioning allegiance to the North Korean state. An extreme form of nationalism, juche functions as a political religion with the government and leader seen as deity and divine. Unlike in a theocracy, where the religious structure has political power, in North Korea, the political structure is the practiced religion. Historically, relationships between religious institution and state have been extremely complex, with power arrangements shifting and changing over time. Today, Christian fundamentalism is playing an increasingly political role in U.S. society. Since its bureaucratization, religion has had a political role in almost every nation-state. In many state societies, religious institutions serve as charity organizations to meet the basic needs of many citizens, as educational institutions offering both mainstream and alternative pedagogies, and as community organizations to help mobilize groups of people for specific actions. Although some states—such as Cuba, China, Cambodia, North Korea, and the former Soviet Union—have declared atheism as their official policy during certain historical periods, religion has never fully disappeared in any of them. Religious groups, however, may face varying levels of oppression within state societies. The Uighurs are a mostly Muslim ethnic group of some 10 million people in northwestern China. Since 2017, when Chinese president Xi Jinping issued an order that all religions in China should be Chinese in their orientation, the Uighurs have faced mounting levels of oppression, including discrimination in state services. There have been recent accusations of mass sterilizations and genocide by the Chinese government against this ethnic minority (see BBC News 2021). During periods of state oppression, religion tends to break up into smaller units practiced at a local or even household level.