Only 16% of people are not religious: in 2018 that's around 1.2 billion people who find it difficult to reconcile the ideas of religion with what they know about the world.
A recent psychological explanation is that our evolution predisposes us to believe in an external agency, and that religion is a by-product of a number of cognitive and social adaptations which have been very important in human development.
- We are social creatures who interact and communicate with each other in a co-operative and supportive way.
- We have stronger attachments to some individuals than others.
- We rely on these attachments during childhood, when making friends and falling in love.
- We can also form strong attachments to non-human animals and inanimate objects.
- These strong attachments can also be transferred to religious deities and their messengers.
Our relationships depend on being able to predict how others will behave in situations and time. But the things we form attachments to don't need to be in front of us to predict their actions. We learn to imagine what others may say or do through childhood pretend play and stories.
We then moved from imagining the minds of other humans to imagining omnipotent, omniscient beings. And religious texts telling of past actions fuels belief.
We are also able to anthropomorphise objects - we see a person when it is just a coat hung on a door, (and our pattern seeking tendencies lead us to see pictures in the clouds, and on slices of toast). We then endow non-human entities such as gods with human qualities.
The ritual behaviour of collective worship makes us enjoy and want to repeat the experience. Dancing, singing and trance-like states are known in many ancestral societies. These social acts, however formal, increase levels of serotonin, dopamine and oxytocin in the brain - chemicals that make us feel good, want to do things again and provide a closeness to others.
Educational and household norms don't tend to dispute religious ideas, but do encourage challenge to early childhood ideas such as Father Christmas or the Tooth Fairy.
The impact of religion and religious thinking on human functioning continues to be the subject of intellectual debate.