5: The fact that religion runs in families.
The single strongest factor in determining what religion a person is? It's what religion they were brought up with. By far. Very few people carefully examine all the available religious beliefs -- or even some of those beliefs -- and select the one they think most accurately describes the world. Overwhelmingly, people believe whatever religion they were taught as children.
Now, we don't do this with, for instance, science. We don't hold on to the Steady State theory of the Universe, or geocentrism, or the four bodily humours theory of illness, simply because it's what we were taught as children. We believe whatever scientific understanding is best supported by the best available evidence at the time. And if the evidence changes, our understanding changes. (Unless, of course, it's a scientific understanding that our religion teaches is wrong...)
Even political opinions don't run in families as stubbornly as religion. Witness the opinion polls that show support of same-sex marriage increasing with each new generation. Political beliefs learned from youth can, and do, break down in the face of the reality that people see every day. And scientific theories do this, all the time, on a regular basis.
This is emphatically not the case with religion.
Which leads me to the conclusion that religion is not a perception of a real entity. If it were, people wouldn't just believe whatever religion they were taught as children, simply because it was what they were taught as children. The fact that religion runs so firmly in families strongly suggests that it is not a perception of a real phenomenon. It is a dogma, supported and perpetuated by tradition and social pressure -- and in many cases, by fear and intimidation. Not by reality.