Fear of the Unknown
Those who were in what we now call the Western world, feeding on flesh and blood, began to fear beyond the horizon – whether it was the horizon within the brain or the world. They began to fear that which they couldn't see, touch, hear, taste or smell. All that which couldn't be defined by those five senses, didn't exist. God, who is not an event of the five senses but an event that produces them from a much greater sensation, had been defined by these five senses – God became a concept, rather than an experience.
Once God had been defined, we had corralled him and put him on a leash. Why is God not listening to me? Why is he not obeying me? Why is God punishing me? All of these questions came about.
It became more than a child playing with a toy, or an imaginary friend.