I often speak of nature and the universe as a whole with language that is mystical and reverential, and it is easy to conflate that reverence and my mysticism as a belief in the supernatural. However, truth be told, I can't say that I have any specified belief in or even much concern for the supernatural.
Because I can experience, experiment, and verify the results of others when it comes to the natural world, it is my focus. Even when I was Southern Baptist, for example, I never had much concern for the issues of life after death. If a deed is motivated by either threats of punishment or promises of a reward, for me, it subtracts a great deal of value from the action — no matter how virtuous. Death is one of life's great mysteries, and it greatly annoys me when people purport to know what happens to the consciousness of a living creature after she dies. No one knows. Knowledge requires certainty and independently verifiable results. One can have faith or belief, but no matter how intense or how deeply held beliefs may be, they are not the same as knowledge.
To be clear, I see nothing wrong with faith or belief so long as knowledge is kept as a very separate concept. I hold a great many beliefs that are ultimately not provable. I speak about them privately among friends and interested parties, but I strive to make sure it's understood that these beliefs are separate from knowledge and empirical data. And in the end, I strive to make sure that beliefs exist complementary to the best evidence we have available. Much like the apostle Thomas, I am not comfortable with mere faith. When decisive evidence contradicts one of my beliefs — no matter how deeply held — I do my best to acknowedge the truth and integrate it into my life.
Many would have you believe that such an emphasis on the natural world and the universe must be as dry and lifeless as the lecture of a bad high school science teacher, but for me, the focus on the natural world allows me to see the magic inherent to the universe itself. Our universe is complex, so complex that it sometimes behaves in very counter-intuitive fashions, and sometimes things that seem extremely improbable over the time scale of a human lifetime turn out to be feasible and even likely over the unfathomably large time scale of our universe.
I accept the reality that this universe is very old — far older than the Earth on which we live. I accept that the Earth and all the elements that make it up were created in the hearts of distant stars through the processes of nuclear fusion and supernovae. I accept that all life on this planet originated from a common ancestor through the process of evolution by natural selection. With no apology, I accept these premises as scientific fact, and this is not a matter of belief but rather a matter of hard scientific evidence. In a very real sense, all of us on this planet are made from "starstuff," and we are all related: you, me, the owl in the thicket by my house, the walnut tree in my backyard, and even the tiny organisms that help me digest my food. In the biology of nature, in the physics of our universe, and in the math that helps us describe the fundamental concepts that govern all things, I find truth, wisdom, and the face of the divine.
I recently saw a decorative plaque that proclaimed in bold black letters "Nature is my church," and I realized that it contained a simple truth that I understood within five years of my birth but which took me over thirty years to truly understand and accept.
Nature is my church, and I am the universe attempting to understand itself.