The brain is a biological organ that many life forms have. Its primary function is to process data from various sensory organs, such as eyes, noses, tongues, etc. Depending on the data, the brain can make decisions as to what actions to take, and because it's wired, through a nervous system to the rest of the body, can invoke muscular activity. In many ways, it's a lot like a computer.
The brain also harbors what's known as the mind, which would be analogous to the software that runs on the computer. Different sections of the brain are responsible for different functions, such as sight, speech, memory and cognitive reasoning.
One way that the brain is not like a typical desktop computer, is that it is a powerful neural net. Instead of having a "processor" that does individual mathematical equations, input data is ran through a network of interconnected neurons in a form of parallel processing. The processing happens due to the weights of the relationships between neurons.
Here is the important point to the neural net model of the brain - The brain is effectively a massive pattern recognition engine.
Pattern recognition is mostly what our brains do.
While pattern recognition is the primary function of our brains, they don't always do this task accurately. One of the amazing capacities of a neural net is the ability to "fill in the blank" when insufficient information is available. Due to this capacity, however, the brain sometimes detects false patterns.
- We see faces in things that aren't.
- We see animals in inkblot tests and clouds.
- We are prone to many optical illusions.
- We will falsely associate one event with another.
The final point is critically important. If, on a few occasions, someone had a good day just when he or she happened to have a lucky rabbit's foot, the person may falsely detect a pattern between "luck" and the rabbit's foot.
In other words, one of the main side-effects of our brains, as neural networks, is superstition.
Relevance to Religious Debate
It could be argued that religion is a set of superstitions that's been codified into dogma and a cohesive social group. Many of the beliefs are kept long after the initial superstitious correlation has been long since forgotten. Some superstitious activities that have emerged within religion are:
- Prayer - association of speaking to an invisible entity, and improved fortunes for the person.
- Faith - association of maintaining a mental state, and improved fortunes for the person.
- Sign of the Cross - a gesture of the hands, and a spoken phrase as a blessing.
In addition to ritual practices, the brain common evokes a mental process known as Anthropomorphism, where human attributes are applied to non-human objects or phenomenon. As a social species, humans are wired to interact with each other. Often, this carries over to the non-human world, sometimes in the form of ghosts or spirits, or in some cases, Deities.
In short, because of how the brain works, we have religion.