That Which Is
The oldest existing reality cannot be called anything more than “that which is”. It is beyond all human comprehension or any attempt at human definition. It is the foundation or fundament out of which the physical Universe we inhabit arose. It is something deeper than merely an Aristotelian “First Cause”. It is that which would still remain even if all levels of physical reality were to be eliminated. It would remain even if there were no space-time or energy-matter. It is quite possible that what I am calling “that which is” has, from our point of view, existed forever and will exist (however the term “exist” might be understood) forever into the future. (Of course, our concepts of past, present, and future are meaningless to that which is, or might be, eternal.) Those who are religiously inclined might view “that which is” as a god or gods of some sort. But given the often anthropomorphic conceptions of gods that humans have devised, or the logical difficulties involved in postulating a god which is both immanent (within every created thing in the most intimate sense possible) and transcendent (above and beyond all physical or temporal boundaries), the attempt to embody “that which is” as a god or gods strikes me as simply another human-originated attempt to describe the indescribable. “That which is” will forever be beyond our limited ability to understand it.
We are part of how “that which is” manifests itself, but we do not live at its level and we are wholly incapable of seeing reality from its perspective, as if the term “perspective” had any meaning in this case.
One can argue that “that which is” must lie within the boundaries of mathematics. I suppose a case for this could be made. It is possible that what humans call, in their various languages, mathematics, are the unbreakable rules by which “that which is” must operate and manifest itself on different levels of organization and existence. But is mathematical reality itself emergent, that is, something which is a level of organization grounded in “that which is”, or is mathematical reality itself “that which is”? (See Is Mathematics the Real Reality?)
Are humans who have experiences which they believe to be mystical or transcendent touching (in some way) “that which is”? Is this the Tao that is spoken of in the Tao Te Ching? Or are these seeming moments of insight strictly the product of a unique chemical circumstance in the brain? Definitive answers to such questions are, of course, impossible to give. About the best we can do, perhaps, is to say that there must be some ultimate reality out of which every logically possible thing emerges, and leave it at that. Beyond that point, we cannot go.