Why do you believe in God? I have been asking people this question for most of my adult life. In 1998, Frank Sulloway and I presented the query in a more official format—along with the question “Why do you think other people believe in God?”—in a survey given to ten thousand Americans. Just a few of the answers we received:

A 22-year-old male law student with moderate religious convictions (a self-rated five on a nine-point scale), who was raised by very religious parents and who today calls himself a deist, writes, “I believe in a creator because there seems to be no other possible explanation for the existence of the universe,” yet other “people believe in God to give their lives purpose and meaning.”

A 43-year-old male computer scientist and Catholic with very strong religious convictions (a nine on the nine-point scale) “had a personal conversion experience, where I had direct contact with God. This conversion experience, and ongoing contacts in prayer, form the only basis for my faith.” Other people believe in God, however “because of (a) their upbringing, (b) the comfort of the church, and (c) a hope for this contact.”

A 36-year-old male journalist and evangelical Christian with a self-rated eight in religious conviction writes: “I believe in God because to me there is ample evidence for the existence of an intelligent designer of the universe.” Yet, “others accept God out of a purely emotional need for comfort throughout their life and use little of their intellectual capacity to examine the faith to which they adhere.”

A 40-year-old female Catholic nurse with very strong religious convictions (a nine on the nine-point scale) says that “I believe in God because of the example of my spiritual teacher who believes in God and has unconditional love for people and gives so completely of himself for the good of others. And since I have followed this path, I now treat others so much better.” On the other hand, she writes that “I think people initially believe in God because of their parents and unless they start on their own path— where they put a lot of effort into their spiritual part of their life—they continue to believe out of fear.”

When Sulloway and I noticed the difference between why people believe in God and why they think other people believe in God, we decided to undertake an extensive analysis of all the written answers people provided in our survey. In addition, we inquired about family demographics, religious background, personality characteristics, and other factors that contribute to religious belief and skepticism. We discovered that the seven strongest predictors of belief in God are:

1. being raised in a religious manner
2. parents’ religiosity
3. lower levels of education
4. being female
5. a large family
6. lack of conflict with parents
7. being younger

In sum, being female and raised by religious parents in a large family appears to make one more religious, whereas being male, educated, in conflict with one’s parents, and older appears to make one less religious. As people become older and more educated, they encounter other belief systems that lead them to see the connection between various personal and social influences and religious beliefs. This helps explain the differences we observed in reasons people give for their own beliefs versus the reasons they attribute to other people’s beliefs.
From the responses we received in a preliminary survey, we created a taxonomy of eleven categories of reasons people give for their own and others’ beliefs. The five most common answers given to the question Why do you believe in God?:

1. The good design / natural beauty / perfection / complexity of the world or universe (28.6%)
2. The experience of God in everyday life (20.6%)
3. Belief in God is comforting, relieving, consoling, and gives meaning and purpose to life (10.3%)
4. The Bible says so (9.8%)
5. Just because / faith / the need to believe in something (8.2%)

And the six most common answers given to the question Why do you think other people believe in God?:

1. Belief in God is comforting, relieving, consoling, and gives meaning and purpose to life (26.3%)
2. Religious people have been raised to believe in God (22.4%)
3. The experience of God in everyday life (16.2%)
4. Just because / faith / the need to believe in something (13.0%)
5. Fear death and the unknown (9.1%)
6. The good design / natural beauty / perfection / complexity of the world or universe (6.0%)

Notice that the intellectually based reasons offered for belief in God—”the good design of the universe” and “the experience of God in everyday life”—which occupied first and second place when people were describing their own beliefs dropped to sixth and third place, respectively, when they were describing the beliefs of others. Indeed, when reflecting on others’ beliefs, the two most common reasons cited were emotion-based (and fear-averse!): personal comfort (“comforting, relieving, consoling”) and social comfort (“raised to believe”).

Sulloway and I believe that these results are evidence of an intellectual attribution bias, in which people consider their own beliefs as being rationally motivated, whereas they see the beliefs of others as being emotionally driven. By analogy, one’s commitment to a political belief is generally attributed to a rational decision (“I am for gun control because statistics show that crime decreases when gun ownership decreases”), whereas another person’s opinion on the same subject is attributed to need or emotional reasons (“he is for gun control because he is a bleeding-heart liberal”). This intellectual attribution bias appears to be equal opportunity on the subject of God. The apparent good design of the universe, and the perceived action of a higher intelligence in daily activities, are powerful intellectual justifications for belief. But we readily attribute other people’s belief in God to their emotional needs and how they were raised.