As to spiritual experiences, feelings, perceptions, I prefer the materialist/scientific explanation to the external deity one. This opinion is probably colored by the fact that the only time I have had such experiences/feelings/perceptions is under the influence of psychedelics.

Psychoactive drugs only work to the extent that they can fit our existing neuro networks, mimicking or replacing neuro active chemicals that our own bodies and brains produce. This strongly suggests that if an experience can be induced by ingested chemicals then the brain architecture and neurochemical signaling systems that create the experience already exist.

There are obvious selective advantages to such feelings and experiences among the small bonded social groups that have dominated most of human existence. These include the preservation of cultural knowledge, the enhancement of critical social bonds, and the satisfaction of our natural ability and desire to see pattern and discern meaning from our surroundings when we are faced with unanswerable questions, such as "what happens to us after we die".