Natural vs Supernatural
What I mean by "Natural" is that which can be explained by the known laws of nature particularly that of biology and physics. And by "Supernatural" I mean that which has no current explanation using known laws of nature. Thus one can partition all phenomena as either natural or supernatural. But this labeling is human centric, i.e. it is subject only to how humans perceive or understand any phenomenon.
Human understanding of phenomena over the ages has evolved from everything being supernatural to almost everything being natural.
During pre-scientific pre-historic era almost all phenomena were considered supernatural. Thunder, lightning, wind and rain were attributed to one or many Gods. Even the act of motion was supernatural. Diseases were attributed to the supernatural. In other words without the benefit of scientific process or scientific thought humans attributed whatever they sensed and saw to be the act of supernatural beings that held enormous sway over the everyday lives of humans. Not only humans but also over other living and even inanimate objects. Mythology dominated over their daily existence.
Then came Philosophy. In the Greek world the leading philosophers were Socrates, Plato and Aristotle. These philosophers tried to provide a less supernatural explanation for phenomena. Their world saw a transition from mythology to philosophy. But they did not entirely discard mythology. They employed what we now call the Socratic method, that of questioning the nature of phenomena and the role of the supernatural. The ancient philosophers provided an opening for reasoning to encroach into the world of the supernatural.
Then came Science. Fast forward to Isaac Newton. By the time of Newton, Science has established itself as an extension of philosophy. The role of the supernatural in explaining phenomena had become severely diminished. I would even argue that the role of philosophy itself had become relatively unimportant in explaining most phenomena. In other words most phenomena by this time have become natural phenomena.
Fast forward to Albert Einstein and the 20th century. By this time the study of philosophy had been relegated to the study of ancient philosophers. Philosophy itself was only nominally used as a label for science only to assuage the egos of philosophers who didn't understand the mathematics and rigors of science.
The baton has passed from mythology to philosophy to science. Today there is very little that is considered to be outside the realm of science. I think only "belief" exists outside science. Even such a nebulous concept as "consciousness" can now be approached with scientific inquiries.
On the biological side, the discovery of cells and the revelation of the DNA has led to natural scientific explanations for how our body systems work. The last bastion to be cracked lies inside our skull, the brain. It is this thick skull that is restricting progress in neurobiology. The mammalian brain is too well protected to yield itself to scientific transparency. But yet it will happen. How we think, remember, deliberate will all be decoded at the intra and inter cellular levels.
Understanding the self is the last step in the journey from supernatural to natural. As the natural expands the supernatural shrinks. The unknowns will become known. The movement of the boundary of the knowns in the field of neuroscience will be fascinating to watch. The philosophers and the theologians might not like this. But as a scientist I am enthralled. One day we will have cracked our own brains. All will become natural as it should be.