All of the philosophy developed herein is grounded in our scientific understanding of the the physical universe in which we exist. It is a materialist, naturalist philosophy, with the scientific method as the ultimate arbiter of objective understanding.
Unfortunately, despite considerable advances, a complete understanding of the nature of the physical laws of our universe remains elusive at this time. While we do have a standard model that provides an accurate description of the fundamental nature of physics, it is safe to say that this model is full of paradoxes and contradictions that render it essentially nonsensical according to the standard expected at every other level of science.
For example, the most widely accepted interpretations of quantum physics are either the Copenhagen interpretation that essentially holds that reality does not exist until measured, or the many worlds interpretation that postulates the splitting of the universe at these points of measurement. The underlying difficulties with the woefully underspecified measurement problem may well reflect a fundamentally misguided framing of the whole endeavor, given the paradoxical and unsatisfying interpretations that result. By contrast, the much less widely embraced de Broglie / Bohm pilot wave framework avoids many of these issues, providing a concrete and deterministic reality at every moment, even when “observers” aren’t looking. However, it also raises other issues that remain unresolved, the discussion of which is beyond the scope of this venue.
In any case, our goal here is to try to avoid any conclusions that depend critically on the quantum level of understanding, while remaining consistent with the overall description provided by the standard model. There is also a corresponding cosmology that provides a reasonable big-picture understanding of the past ~13.8 billion years of existence in our universe, but it too has a number of limitations regarding our understanding of space, time and the potential future and past outside of this known window. Thus, with all appropriate caveats and context, let’s proceed to the key issues at hand.
Bare physics itself
To begin, our initial objective is to try to strip away all of our subjective, abstract, cognitive-level conceptions of the world, and picture what the “bare” physical world is really like, all by itself, without any cognitive observers around trying to understand it. It is only by attempting this seemingly impossible feat that we can begin to understand the difference between our subjective cognitive abstractions and the “true” underlying nature of physical reality itself.
The picture I formulate in my mind is one of complete darkness, filled mostly with empty space, with some kind of buzzing blobs of energy zooming around corresponding to electrons, quarks and the whole lot. When you zoom down real close, each point in space is impossibly far from every other point, and “particles” (which act like waves) are significantly further way from each other than the planets are from the sun, if you scale the sun to the size of a proton (i.e., a hydrogen nucleus).
There are no “things” in this universe, and there is nothing but the immediate present moment of time, because constructs like “things” and the “past” require the ability to compare across space and time, which is not possible at this bare level. It is just raw stuff buzzing around endlessly, following some kind of force fields permeating space. You cannot even measure anything at this level, because to do so would disrupt the system you are measuring. There is no distal perception like vision: everything is entirely local in space and time.
Due to the Pauli exclusion principle, atomic and molecular elements cannot occupy the same space-time location as each other, so everything in the bare reality has its own unique spatiotemporal existence (i.e., its own timeline) separate from everything else. It is an exceptionally lonely and isolated place, from the usual human perspective.
Any two clumps of matter physically cannot be identical in all respects: they at least occupy a different physical spacetime location, and almost certainly have unmeasurably different states of their atomic constituents.
Everything in the bare physical universe is unique unto itself, a “one-off”, simply existing autonomously in its own ever-present now, and here.
Thus, the most basic concepts of identity, similarity, differentiation, categories, and persistence over time are all revealed to be constructs of the cognitive observer: they do not exist as such in the bare physical universe.
Epistemology and all that
The major foundations of philosophical thought wrestle with the steps involved in going from this bare physical universe to the familiar world of objects and concepts that fill our subjective experience.
From a modern, neuroscientific perspective, the answers to such puzzles are to be found within the neural structures in the brain that are shaped via learning mechanisms over many experiences, to form the mental representations as distributed patterns of neural activity that we as human brains subjectively experience as thoughts in our minds. As this is the primary focus of my scientific research (i.e., the “day job”), it is not a focus here. It suffices to say that computer simulations of these mechanisms are capable of extracting statistical and predictive regularities from the sensory world to reliably form similar distributed representations across individuals with similar overall brain structures and mechanisms.
When raised in a culture with language and a foundation of scientific knowledge, our brains develop enough of a systematic basis set of concepts to understand the words in documents such as these, and so we get on with it from there.
It is all in your head, but it is NOT arbitrary!
To this point, we have established that everything above the bare physical level is in your head, not “out there” in the world in any manifest way.
However, just because this understanding is in your head, it is not therefore arbitrary or completely up to your own subjective whims to describe in any way you see fit. In general, there is a strong tendency to overreact when some initial ideal, like some kind of automatic access to the physical truth, is invalidated: we need to learn to embrace the grey.
Some ways of understanding the physical universe have better predictive validity than others, and the process of science is all about refining our objective understanding to generate more precise, accurate theories about how it all works.
This objective knowledge is “real” in the sense that it provides a good, predictive account of how reality behaves, but it is not “real” in the sense that it somehow comes directly into our brains from the physical universe. Constructs such as “electrons” and “electromagnetic force” are theoretical tools we use to describe the behavior of the physical universe: they are what they are, and we are just trying to accurately describe them using concepts in our brains.
Considerable experimental evidence strongly supports the idea that the same physical laws operate everywhere in the observable universe, and the standard model, despite its various limitations, strongly suggests that there are a finite set of such laws that can explain how it all works. Thus, it does seem that the physical universe can be understood to some level of completeness: it is not some kind of random thing with “magical” properties that have no explanation.
Comparison, similarity, and categorization in a one-off world
Any attempt to posit that “this thing” is the “same” as some “other thing” violates the bare physical reality that everything is its own unique blob of matter. No two physical entities (composed of fermions) can ever be completely identical (they at least have different spatiotemporal timelines), and the individual constituents are exceptionally unlikely to be precisely comparable in any way (measurement issues aside) as the systems get to the macroscopic sizes that we can actually perceive and directly understand. Furthermore, any more complex such combination of molecules is exceptionally unlikely to ever be identical to itself at a prior moment in time, given the ever-evolving nature of the physical components and their relationships to each other.
Thus, any attempt to assert that two things are “the same” necessarily must be qualified relative to an abstract, mental category based on some kind of criteria, that always involves at least some “rounding error”: differences that we just ignore because they are small relative to the main dimensions of interest.
We can posit that two objects have the same mass, or size, or color, or various other such properties, but it is literally impossible for any two objects to be the same in all respects, and most of these other more limited claims are only approximately true, at least due to the limitations of quantum measurements, if not due to more prosaic macroscopic measurement errors.
Thus, any attempt to postulate natural categories of things in the world is subject to these limitations: all such categories are necessarily approximate (except at the most basic physical level: it is highly likely that all electrons are identical except for certain well-specified properties such as their spatiotemporal location). The category of human brains or people is a rough collection of individuals, each entirely unique in their spatiotemporal timeline and physical configuration. Although we are prone to want to generalize across such categories, it is important to be aware of this fundamental imprecision. And any thought experiment that requires two “identical” people except for some specific property is entirely suspect.
Because the underlying state of any given physical system is always changing over time, all of these points apply to any attempt to categorize that one system itself. A “thing” is not really a “thing” at the bare physical level. This is apparently an issue that philosophers have wrestled with.
All of these points play a critical role in the foundational issue of emergence, which depends critically on the ability to compare across multiple different physical instantiations of complex physical systems. It is only when we engage in this comparison that we can establish that an emergent phenomenon depends on some higher-level properties of physical systems, and is not directly reducible to just the “sum” of its parts. Furthermore, a defining property of emergence is that multiple different physical systems can give rise to the “same” emergent phenomenon, as in the example of a system of gears composed from different materials.
Thus, we conclude that emergent phenomena are entirely a construction that we impose onto the physical world, and they do not exist as such at this bare physical level where no such comparisons are possible. But again, they are not arbitrary, and are subject to all the constraints of objective knowledge per above.
And yet, due to the constantly changing nature of any macroscopic physical thing, everything that we think about at this macroscopic level is effectively an emergent phenomenon: there are certain properties that we use to define the relevant nature of the thing in question, and we consider it to be the “same” thing so long as those properties still hold, as an invariant property of the thing relative to its ever-changing underlying physical substrate.