Approaches to distinguishing religion from non-religion can be divided into two broadly defined schools of thought: function-based approaches and form-based approaches.

Religion is subject to much discussion in the fields of theology, psychology, sociology, and anthropology. Specialists in these fields, as well as ordinary people— theists, atheists, and agnostics alike—often disagree about the fundamental nature of religion. Consequently, any discussion of religion must begin by answering certain "basic" questions such as "What is a religious belief?", "What is the difference between religious and secular beliefs?", "How do we recognize what are religious beliefs?", "Are religions individual or group activities?", and "What methodology shall we use to investigate these questions?". The answers to these questions and similar questions can then serve as a common ground upon which further discussion can be based.

If the conclusions of a discussion are to be accepted by people from diverse religious backgrounds, then that discussion must make as few assumptions as possible. However, this article starts with the following a priori assumptions:

• There are sets of beliefs that are "religious".

• These beliefs are distinct from non-religious beliefs and recognizable as "religious".

• (The most controversial) There are ways to recognize which beliefs are "religious" and which are "non-religious".

The last one is most controversial because there are two main ways of looking at the world, each bringing with it certain a priori assumptions that are usually not recognized. While a study of a particular religion made by either viewpoint may come to many of the same conclusions, differences between the two approaches include what beliefs are to be considered religious and the effects of religions.

By function

One approach, sometimes referred to as "Hebrew thought ", defines "religion" as any set of beliefs that fulfills certain functions in an individual’s life, especially answering questions about our origins, present existence and where are we going and how shall we get there?, thereby forming the individual's attitudes, values, morality and actions. Consequently, adherents of this approach regard any belief system which answers any of these questions as "religious", including such non-theistic belief systems as Communism, secular humanism, and biological evolution.

The main advantage of this approach is its ability to incorporate seamlessly all of the belief systems that are considered religious, including some of the agnostic forms of Hinduism and Buddhism; according to its advocates, another advantage is its recognition of the fact that the phenomenon usually perceived as conflict between “religion” and “anti-religion” is in fact competition between different fundamentalisms.

One difficulty in applying this approach is the fact that many individuals hold multiple belief systems, some of which may be contradictory, and some feigned; consequently, it is often difficult to recognize the effect that any particular belief system has on an individual. Another difficulty is that it tries to evaluate what act as the inner guiding principles within an individual, his "religion" as it were, by the fruits those principles produce in his attitudes, values, morality and actions. It does not necessarily consider those beliefs and associations he admits to in public. Though this is a difficulty, it can be used to identify those who truly are adherents to a particular religion versus those who merely join the organization for reasons other than belief.

When studying specific religions or comparative religions, a functional study typically starts with an analysis of the teachings of the belief system, which includes an analysis of the "sacred writings" connected with the belief system if they exist. In this analysis, attention is paid to internal consistency, to whether or not the belief system answers the basic functional questions of origins, ontology and teleology, how well it correlates to observation and how it guides an individual's attitudes, values, morality and actions, even how he thinks. It looks at how integrated the religion is with daily life: is it merely ritual that once acted upon can be forgotten as done, or is it a belief that should inform every action an individual does?

A functional study also looks at those who claim to follow the religion to see if they truly follow it or not, and why.

Questions concerning group beliefs, actions and institutions, though important, are secondary because they are a result of doctrine and individual response. They may actually represent cultural norms and institutions rather than individual belief and practice, so that though they may appear to be a religion, they really aren't.

Some social scientists, such as Emile Durkheim, emphasize the social aspects of functional forms of religion, as a means of providing social cohesion and community. Other social scientists now define religion by its consequences not in social life but in the personal life of individuals. These authors define religion as “a combination of forms and symbolic acts which relate the individual to the ultimate conditions of his existence." (Richard Bellah, “Religious Evolution”, 1964, p. 358), or as “a system of beliefs and practices through which a group of people faces the fundamental problems of life.” (Yinger, J. Milton, "The Scientific Study of Religion," Macmillan, 1970, p. 7)

This approach is also illustrated by the 4th definition of religion in Webster's Online Dictionary, which defines religion as "a cause, principle, or system of beliefs held to with ardor and faith."

By form

Also called "Greek thought ", it is the method most widely used by far. It is almost universally used in academia and among sociologists, anthropologists and Western philosophers.

Most people, particularly those influenced by "Western" culture, almost instinctively recognize which of their beliefs are to be called "religious" and which "secular". Usually unconsciously, they have already made a priori assumptions such as "There are beliefs that are 'religious'", "Religious beliefs are not the same as secular beliefs" and typical assumptions imparted by western culture to recognize "religious" beliefs include:

• A belief is religious if it is labeled as "religion" by those who believe it.

• A belief is religious if it deals with "spiritual" matters.

• A belief is religious if it results in ritual practices designed to invoke a higher reality, examples include prayer and worship.

• If a belief is agnostic or atheistic and does not result in ritual practices, it is "secular".

• If a belief, organization and rituals associated with them are not intended to promote a "religious" teaching, then they are "secular". Secular political parties in secular government with their beliefs and rituals are examples of secular organizations.

• If a belief is "scientific" then it is secular.

When studying specific religions and comparative religions, discussions typically begin by answering questions about uncontroversial, easily verifiable facts, such as "What beliefs do different groups of people hold?", "What practices are inspired by these beliefs?", and "What institutions arise as a result of these beliefs and practices?". Hopefully, answering these questions will create a body of data upon which all further discourse, including the answers to the "basic" questions mentioned in the first paragraph of this section, can then be based.

One advantage of this method is that people who hold to agnostic and atheistic belief systems can decide for themselves whether or not what they believe is a religious or secular belief system. Another advantage is that it conforms to widely held societal and academic norms, aiding in communication. Thirdly, in that it conforms to societal and academic norms, it avoids misunderstanding and conflict that can arise when using minority approaches, such as the functional approach above.

In contrast to the functional approach, the use of Greek thought as the methodology to study religion, with its emphasis on the inherently uncontroversial statements about religion's external manifestations, its expressed statements and rituals, is far less controversial and easily recognizable, therefore are more readily accepted by people with widely differing views of religion. Consequently, most major thinkers prefer to begin by examining the easily observable external forms of religion.

This approach is also illustrated by definition 1b of religion in Webster's Online dictionary, which describes religion as, "the service and worship of God or the supernatural."

Practical examples

The question how to distinguish a religion from a non-religion is not just a theoretical question. In the case of Scientology it has been disputed in court, for example in the Netherlands. Classification as a religion gives tax privileges. Scientology's critics claim that it is a business and not a genuine religion. See Scientology controversy.

Discordianism has been described as both an elaborate joke disguised as a religion, and a religion disguised as an elaborate joke. Some of its followers make the claim that it is "a religion disguised as a joke disguised as a religion." Episkopos Aloysius Thudthwacker in this article has pointed out a few similarities between Christianity and Discordianism. Some Discordians have described Discordians as Taoists with a strange sense of humor and the inability to sit still. The reader is welcomed to try their hand at determining what Discordianism is for it is a very difficult case study to discern.