For me, the knowledge that I will someday return to the good Earth of which I came is enough. All humans depend on the very elements of nature to survive. What better purpose than to decay into the soil again? Fear of mortality is hatred of nature. Nature is, if indeed there can be, the personification of god. Its vast connected elements of the physical matter such as soil and water entwine with the less visible synergies and tiniest of particles that are a part of the larger whole. What are the promises of and fearmongering of old stories compared to the wholeness of nature, but a metaphorical and transcendent experience on paper? An entry point that frees are left brain and ability to feel outside ourselves. Our destruction of nature is a sign of this lack of ability. On the other hand, nature, science, and spirituality are all connected in that they exist in the same world. Science is a process of discovery created by humans to explore nature, but tis not the only knowledge paradigm. As humans with a conscience that other animals don't possess, we may evolve into different ways of thinking and being. Though it is up to us individually to decide how we use these abilities or whether we choose to look beyond whats right in front of us. Perhaps humans may evolve physically as well as spiritually.
But if humans are indeed a part of nature then we are not superior or any different from the other animals inhabiting this plane of existence. And our purpose in life is to simply live and return to the Earth of which we came. Does that mean we our necessary to nature or would it be just fine without us? Its the second, of course. Human existence is one of constant need despite our awareness capability to rise above a destructive life. But this is exactly the problem, but other animals prosper contently in their slavery to instincts. Perhaps another purpose to life is for humans to better ourselves thus the world around us. Or we could simply life by laws of land as we should do anyways. Though its morally prudent for anyone to think that alone makes for a life of purpose.
So what are these other planes of existence? Why would we even need them anyways? To answer these questions one would have to push aside the right-brained materialist denial that so dominates our world today. Is reality subjective, what of the possibility that what we think we know is not our own knowledge (we our not in sole possession) or it may not even be real? Was not science a method invented by humans to understand and organize the natural world just as religions use to make up myths to explain the world? Whether the goat be horned and tail and movement explained by laws of gravity and water merely chemicals we realize humans are not the center of the universe. In "planes of existence" I mean the awareness of potential places both in this world, within ourselves, and any spiritual dimension. A "god that exist in everything".