What is a "Natural Religion"?

One issue associated with the sociological study of religion is the distinction between ethnic and universal religions. Ethnic religions may also be called "natural" religions while universal religions may be called "voluntary".

Generally, a natural religion means one is a member by virtue of being born into it. Membership need not be limited to believing something. In contrast, a voluntary religion demands a certain intellectual assent of the basic doctrine of the faith before one can really be considered a "member". A natural religion is one that is closely tied to culture and ethnic heritage - it is what one is not merely what one believes. A natural religion is a part of one's personal identity. Another way of referring to natural religions is to call them "ethnic religions".

Most of us are raised and taught a certain religion and may or may not accept it. It is easy to reject a voluntary religion - you simply reject the belief. But a natural religion is near to impossible to entirely reject. One may choose not to believe and not to practice but culture is a part of it as well and one cannot reject one's cultural heritage. (There are people who would identify themselves as "Jewish" but do not believe in God or practice the religion. For them, Judaism is a culture, not a religion). By way of comparison, if you are born an American and you move to another country, you are still an American. Being American is part of our cultural heritage and that we cannot change. But if you are raised in the Methodist church and move to another church you would no longer be a Methodist.  Being Methodist or Christian is really something that is supposed to be a matter of personal choice (the choice to follow Christ) - thus "voluntary". While you are free to change churches or reject Christian faith altogether (thus voluntary) you can't really get away from your American cultural heritage or stop being "Black," Hispanic, or Asian (that's "natural"). 

Christianity is a religion that is independent of culture or race (thus "universal"). Other religions are intimately linked to such things (thus "ethnic"). A "natural" religion is like race or ethnicity - something you can't entirely get away from. And, like ethnicity, natural religions tend to remain limited to a particular people. They do not actively seek converts and it is difficult, if not impossible to convert into a natural religion. Again, one has to be born to it. In contrast, voluntary religions tend to be much more diverse as they have intentionally "spread the word" to all corners of the globe with no concern as to the cultural heritage or ethnic background of the followers. 

A student asks: "Why do ethnic religions not seek converts to their religions?"
Well, they just don't feel it is necessary. They do not see it as a imperative to "save" others with "their" truth. They are not "exclusivist" about Truth or that everyone should live by their rules. Imagine Native Americans insisting that non-Native Americans should adopt the Native American religions. Or the Chinese insisting that Americans speak Chinese. Ethnic religions, like languages, belong to specific groups of peoples. If one is not part of that group, one is not expected to follow the religion. One is expected to follow the religion that is native or "natural" to one's own group.

Another distinction between natural vs. voluntary is that natural religions tend to think in terms of group salvation while voluntary religions tend to think in terms of individual salvation. Christians should be able to see quickly how their religion is voluntary: each individual is saved, whether the community is or not does not impact on the individual's salvation. The communal concerns of natural religions makes sense given their tendency to be bound by culture and ethnicity. Newer, voluntary religions tend to universalize what natural religions keep to their own group. Christianity made universal what Judaism kept within it's ethnic group. Islam unified the Arabs under one religion rather than the tribal divisions that pre-dated Islam. Buddhism took the spiritual wisdom of India and spread it throughout Asia and beyond.

Natural religions also tend to be older than voluntary religions. The original (oldest) religions were natural/ethnically linked where everyone in the society was automatically a follower of the religion of the society and there was only that one religion in the society (think of the religions of ancient Greece, Rome and Egypt - or the religions of the Native American Indians). Voluntary religions essentially have individuals choosing to follow some religion other than that of the social norm. In addition, unlike the relatively newer voluntary religions, natural religions do not have a particular founder. Their origin cannot be pinpointed in history. These religions simply developed gradually, over many generations dating back to pre-history. Just as no one "invents" a culture, so no one "founds" (starts) a natural religion. These are religions that were already present when the history began to be recorded.

The above distinctions do have exceptions (there are, for instance, black Jews and Western Hindus), but in general, the bulk of followers of a natural religion will come from the same cultural background.