The most popular religion in the world is Islam with over 1.6 billion followers worldwide and 25 countries that recognize it as their official state religion. Christianity comes in second with over 2 billion followers, followed by Hinduism and Judaism. Whether or not you believe in any of these faiths, it is safe to say that most people think that their religion is the best one.
It is important to understand that, although many scholars have argued for functionalist definitions of religion, the concept is a social taxon. This means that it has the power to sort cultural phenomena into different categories. This makes it hard to discuss whether or not a particular phenomenon belongs in a religious category. Using a functional approach also raises philosophical issues that do not arise for other abstract concepts used to sort cultural types (such as “literature”, “democracy”, or even “culture” itself).
Some philosophers have tried to avoid these problems by arguing that it is possible to define religion in terms of certain structural features, without referring to mental states at all. They have called this approach “polythetic.” However, polythetic approaches also run into the same philosophical problems as a traditional monothetic view of religion.
Moreover, the debates over whether or not to include the idea of religious beliefs as part of a definition of religion have largely been inconclusive. Ultimately, it is unlikely that we will be able to agree on an adequate definition of religion.