I can say for myself, I know for a fact from my experience Demons, Spirits, Non-Physical Entity's, whatever you may call them, do indeed exist. Why wouldnt the Divine/Source permit it anyway? When one's awareness is grounded into the relative level of consciousness, technically "anything" already does exist within the microcosm of God as Infinite Potentiality. As For Mother Nature, She is Objective, Nature being objective within this reality framework to be precise, no doubt this planet is crawling with the unseen spirits.

It can just be difficult to tell an etheric being from one from the mental planes(astral).