What reality is is essentially what reality does. If science has a foundational first principle this comes pretty close. There is no need or point in looking beyond the behavior of bodies in the world. Via universal common sense it is already known what a body is and so we only need to determine what it does under varying sets of conditions. Based on the way science must look at the world, it can not penetrate deeper than this without the risk of crossing the threshold into transcendent speculation.
People share a common sense understanding of what reality is and what is meant by being in the presence of an object. We can see it, hear it, feel it, smell it, and taste it. We sense the its of the world, and the its of the world cause our senses to react at the appropriate level of their natures. We look at the table in front of us; we rap our knuckles on it. Even though we may argue about the nature, essence, or definition of the term "table", most people with normal sensory abilities accept that they are in the shared presence of the object.
But what "is" the object? What fundamentally causes it to come into and remain in being? Persons of a transcendent bent say the cause is God, the gods, consciousness, mind, spirit, etc. Granted there is no evidence of such forces in the objects themselves. However, perhaps it is not necessary for causes to reveal themselves in the caused.
As Thales argued from the very beginning, our journey of understanding the mysteries of the world must start somewhere. He reasoned that because of the problem of infinite regress one ultimately must begin with something which is self-caused. For him it was water, i.e., the objective, material world. We all share in the water, experience it in essentially the same way, and it seems real onto itself. Since we can not universally detect any substance or cause prior to water, then it seems to be the self-causing substance which causes everything after it to exist.
Still, there may very well be prior causes for material reality that would take us into the realm of the transcendent. But, as far as we can observe, there is no direct evidence for this in the material nature of reality as we conceive of and understand it. Of course the scientific or materialist mind can not prove the negative that a transcendent reality does not exist and that it does not cause sensible reality to exist. But it can say, and has said since Thales, that if we are to look for first causes, then we need look no further than among the things we can hope to know via our senses and reason. The most obvious thing we can hope to know is water, i.e. material reality. Until there is evidence to the contrary, this would seem both reasonable and sufficient.
Materialists and mystics look at reality in essentially the same way. With the possible exception of Christ, everyone and everything seems to conform to the laws of substantial material nature. Many people claim to experience events and realities beyond this. But such experiences are not or can not be shared with others. However mystical, rational, or psychotic, people have never done anything other than conform to the material rules of reality. To the best of our knowledge no one has ever been observed walking through walls.
To a large extent science is justified in dismissing speculation when it makes scientific or pseudo-scientific truth claims. But by the same token, when science takes a "what it is is what it does" position, then it too is engaged in what amounts to transcendent speculation. It is establishing a ground for what it can not ground via the rules of its own epistemology. Because the boundary between science and speculation is along the is/does line, science can only attempt to determine what reality does. It can not legitimately make any truth or meaning claims about what reality is.
There may indeed be whole new levels of knowing awaiting us in the realm of the transcendent. But scientific reason presumably can not expand its foundation of knowledge in this direction. It does not as yet have the tools for access, and we may not have the mental power needed to understand such things. So why even bother when the effort can yield nothing of value or meaning?
Ironically, even though science and rational investigation denies such things, the project is nevertheless in a sense metaphysical because its explicit grounding is itself ungrounded and its implicit grounding has also never been seriously challenged or thought through. Science makes knowledge claims that reality is material, self-contained and self-animated based on what amounts to sufficient knowledge: here are the objects of existence all around us, and as far as we can tell there are no transcendent substances attached to them. It insists on what can not be asserted based on, of all things, faith and the fact that it has built a world view that yields powerful technology and great human material progress. It assumes that because it generally understands what reality does that this is sufficient for knowing what reality is. It insists that reality is only material because its explicit and implicit assumptions can only draw this conclusion from the way the evidence is looked at.
People of science tend to misunderstand the nature of their project. Their consciousness of what they are doing has become historic and thus somewhat unreflective of certain basic assumptions. Such reason looks at reality in a very specific way that has never been seriously challenged except by transcendentalists - who are now for the most part ignored. The transcendentalists have been dismissed because they too look at the same reality in essentially the same way and speculate or will that there must be unverifiable entities or forces that cause or participate in the reality. We move in very tight circles of constraining ideas.
