II. There are good reasons to be SKEPTICAL about religion and religious beliefs.
A. Religion is NOT the key to Happiness and Virtue, contrary to common belief.
B. Significant Disagreements exist Between Different Religions.
C. Religious Beliefs are Typically Based on Cultural Bias and Social Conditioning.
Religious Beliefs Are Associated with Geographical Locations
The religion of a person can often be accurately predicted based on where they were raised. For example, if someone was born and raised in Saudi Arabia or in Turkey, it is almost certain that he or she is a Muslim, because nearly 100% of the populations of those countries are Muslims. If someone was born and raised in the Honduras, Venezuela, or Bolivia, it is almost certain that he or she is a Christian, because nearly 100% of the populations of those countries are Christians (in fact it is highly probable that such a person is a Roman Catholic). If someone was born and raised in Cambodia or Thailand, then it is highly probable that he or she is a Buddhist, because about 95% of the populations of those countries are Buddhists.*
If someone was born and raised in Norway, then it is highly probable that he or she is a Christian, because 98% of the population of Norway are Christians (in fact it is highly probable that this person is a Lutheran). If someone was born and raised in Greece, then it is highly probable that he or she is a Christian, because 98% of the population of Greece are Christians (in fact, it is highly probable that he or she is a Greek Orthodox Christian). If someone was born and raised in India, then it is very probable that he or she is either a Hindu or a Muslim, because 81% of the population of India are Hindus and 13% are Muslims, so 94% of the population is either Hindu or Muslim.
There is more of a mix of religions in the USA than in most of the countries I have mentioned above, but Christianity is clearly the predominant religion, and “nones” (non-religiously-affiliated people) are the next largest group in terms of “religious” identification. So, if all you know is that a person was born and raised in the USA, you can reasonably predict that this person will either be a Christian or a person who has no religious affiliation, because 71% of the population of the USA are Christians and 23% are nones, so 94% of the population in the USA are either Christians or nones (http://www.pewforum.org/religious-landscape-study/).
Religious Beliefs are Typically Based on Cultural Bias and Social Conditioning
Another relevant fact is that people do NOT typically carefully study a wide variety of religious and secular viewpoints and then decide which one to believe and practice. It is true that a few people do this as adults, but they are a tiny minority. Most people simply accept the religion (or the secular viewpoint) of their parents, or the predominant religion/worldview in their ethnic group or community or nation. Religion is typically a matter of GROUP THINK, of accepting a point of view without doing any serious investigation and inquiry. It is sad but true that the most important beliefs we hold are typically adopted without doing any serious thinking. The alternative to doing a serious comparison between alternative religions is the path of least resistance: believe and practice the religion that is most common in your ethnic group or community or country.
One more bit of evidence confirms my thesis: religious people are usually skeptical about the beliefs and practices of other religions, but not about the beliefs and practices of the religion they were raised to believe and practice. Theists, for example, reject belief in thousands of gods, but believe in just one infinite god, the one god that their culture and upbringing promotes. Christians are skeptical about the existence of various gods worshiped by polytheists.
This appears to involve use of a double-standard. We either need to indiscriminately accept ALL religions on the basis of little or no evidence, or else we need to be skeptical about ALL religions. We either need to accept belief in ALL alleged gods and supernatural beings on the basis of little or no evidence, or else we need to be skeptical about ALL gods and ALL supernatural beings (This is a point that John Loftus rightly emphasizes in his book The Outsider Test for Faith).
Because it is clear that religious beliefs are typically based on cultural bias and social conditioning, we have GOOD REASON to be skeptical about religion and religious beliefs.
* The statistics I give on the religions of populations of countries other than the USA are from this source: