“…metaphysics can indeed be about reality, and can avoid collapse into empirical scientific theory, provided we can learn to be content with the fact that, as far as actuality is concerned, metaphysics cannot provide us with certainties” E.J. Lowe The Possibility of Metaphysics (1998)
The central question of metaphysics might well be “what must be true to make the universe we experience possible?” As E.J. Lowe puts it in the aforementioned book “… metaphysics has been thought of as the systematic study of the most fundamental structure of reality…” The experience to which I refer includes all that we take to be an external world impinging on our sensory systems, but also the fact of experience itself, that all that impinging has a subjective result, a “something it is to be like ourselves”. In its turn, a part of that subjective experience seems to include a power, an ability on the part of the subject, to effect events in the external world without such actions being either chance occurences or ridgedly determined by antecedent events. It is not controversial that such impact is effected through the movement of a body, but from the subjective viewpoint, such movement is but the terminus of a process initiated by what appears, literally to our selves as a self, that again subjectively, appears not to be merely identified with a body, but a controler of it.
It is the present fashion in both the sciences and philosophy to claim that what appears to be a free and extra-material controller of a material body is but an illusion. Similarly, the subjective arena in and with which the controller seems to function is also declared to be illusory. There is somewhat more sensitivity in the latter claim to the matter of how it is that an illusion can appear to be something to itself? Mostly these viewpoints amount to a modern version of nihilism, but their proponents claim to be doing nothing more than following out the logical consequences of physics, that is the discoveries about the external world (the one that impinges on our senses and of course including the senses themselves) that physics has revealed. This is a disengenuous claim. Proponents are assuming that the only explanation that can be provided, and by this I mean as concerns both the objective and the subjective, is the one that physics is able (if not now than ultimately) to provide. No other explanation can count for anything other than fantasy if it is not expressible in physical terms.
This “naturalistic error” becomes quickly associated with a “physicalist error”. Because the technological results of scientific methodology at least do strongly suggest the validity of our conclusions concerning the physical world (with a few controversial “edge cases”) and coupled with the observation that a methodology employing physical instruments can only detect physical phenomena, one reaches for the conclusion that the physical must be all there is.
Physicists and philosophers who are worth their Ph.D’s all admit that this reach is an assumption. They know that there is no logical proof of the being, or not being, of anything real in the universe that is other than physical. So why this insistence of a declaration of naturalism (no explanation other than science) and physicalism (nothing but the physical exists) on the part of so many otherwise well educated people? The reasons are mostly negative. Beginning with the assumption that “there is more than the physical” that is real, philosophers have for centuries offered answers to the fundamental question (what must be true for all of this to exist) that, while they might answer the question, simply cannot be confirmed as the true or best such answer. Put in technical terms, experiential evidence (including that of physics), underdetermines metaphysical theory. In non technical terms this means that more than one such complete explanation can work and there is no objective methodology that can be used to pick out the right one.
Physics as such has reduced the ultimate question to “what must be true to make our physical world, implied by the macroscopic (and deterministic) reality we experience through our senses, the way it is?” This is a perfectly legitimate question and physics has discovered much of what lies beyond our natural (that is biological) senses forming parts of the answer to that question. That these explanations are real answers and that they are complete answers is demonstrated, again via our senses, by the fact that technology grounded in the consequences (philosophically speaking “necessary corollaries”) of those explanations actually works! Not only does it work, but we can predict to an extraordinary degree of precision how alterations in material inputs will affect (that is alter) their outputs! This means that any further explanation, any explanation that entails anything beyond or besides physical inputs, is redundant.
There do remain a few edge cases, places where our physical explanations have, at least for the moment, run up against a wall. An interpretation of quantum mechanics is perhaps the most famous of these, but the completion of the standard model, in particular the basis of gravity and its capacity to warp space is another as is the origin of life, and the genesis of the big bang. What these questions have in common is the shared, universal assumption on the part of physics, that the answers to them will form a self consistent set and that they will prove to be strictly physical making non-physical additions redundant. Interestingly though, it is with physics here at these limits exactly the same as with metaphysics in that our evidence, the evidence with which we seek to discover the answer to what must be true, underdetermines theory. As with metaphysics there are multiple possible explanations that account for the physical evidence and at the moment we have no definitive way of choosing between them.
Then there is the matter of consciousness, the observers at the end of the chain seeking the answers to all such questions. On this planet at least only humans appear to be observers of this kind. There is a general acceptance of higher animals (at least) being conscious in the sense of having a “something it is like to be” experience. But none of them (and indeed not all humans) appear to ask or care to look into the fundamentals of that experience. Still, only humans ask these questions, and only humans direct behavior towards answering them.
As an edge case for physics the matter of consciousness poses a special problem. No one denies that consciousness in some sense exists in the physical universe. But it is not, like the other edge cases, so obvious that the answer to the “what must be true” question would or could be purely physical, leaving no room for a non-redundant, non-physical component of the answer. Most physicists and philosophers today simply assume that, like everything else that physics has discovered, this limit too will ultimately prove to have a purely physical explanation. But this reasoning ignores the fact that physics can detect only the physical whether there is anything else in the universe or not; we are returned to the physicalist assumption.
Even if physics happens to be wrong concerning physicalism, metaphysics, some explanation for both the physical and the non-physical cohabiting the universe, will be unhelpful unless there is some means by which we can narrow metaphysical possibility. Underdetermination is a problem whenever the observers reach, temporarily or otherwise, some explanatory limit. Physics has a methodology (observational, mathematical, and experimental) it applies to limit the range of possible explanations though as I will show in part II the edge cases, even apart from consciousness, are often, even in principle, beyond such treatment. Even where applicable, math, experiment, and observation might not serve to pick a single explanation, but they do limit the reasonable candidates. Not all theories qualify. For metaphysics to be reasonable the same consideration must apply. There may be no method by which a single metaphysical theory can be identified as “the true answer”, but there should be some means to narrow the candidate field. Science is about what happens, while metaphysics is about what is possible.
Metaphysics has one tool analogous to mathematics, that being logic. But the validity (in the sense of being true of the actual universe) of both logical deduction and induction rests on the truth of assumptions and those assumptions (and this is just as true of physics) are made only by observers having subjective experience, the very experience whose inclusion in the universe for which we are trying to account! In turn this means that besides logical consistency, the only limiting methodology available to metaphysics is experience itself; that is a correct apprehension of it. Metaphysics must account both for physics and subjective observer experience as concerns both the fact of the latter in the universe and its content. Metaphysical answers must not be inconsistent with physics and at the same time, they must account for both the appearance of the non-physicalness of consciousness and that of free will. They must also account for all that manifests in the consciousness of observers; not merely qualia but also ideas, intension, meaning, and value.
This sets up something of a built-in circularity to metaphysics. What must limit its speculation is the very experience we are trying (among other things) to explain. The facticity of these phenomena and their purported non-material nature is the very quality open to question. To avoid a patent circularity, metaphysics must, like science, modify the central question. Not what must be true for the world to be as it is, but what must be true of the world for it to appear to us as it does. That would include the appearance of subjectivity and especially free will without presupposing their facticity.
Metaphysics has from this requirement generally suggested two broad sorts of answers to the “what must be true” question; either monism, or dualism. The physicalism already sketched is one form of monism. It argues that there is only one kind of thing in the universe that is real, the physical, including everything from the microphysical quantum universe to spacetime curved by gravity. Anything that appears to have some non-redundant non-physical aspect is only an illusion. But an illusion is a subjective phenomenon. An antecedent subject is presupposed and that cannot be an illusion because some subject is experiencing it. Physicalists have argued that the subject itself is the illusion but then who or what is it that makes this claim? Non-subjects (like rocks or statues) do not have illusions, and it is for this reason that physicalism gets around eventually to a nonsensical nihilism in which the subject making the claim denies not only his own experience, but by that the meaningfulness of the claim of illusion. As with illusions, only an antecedently existing subject can experience meaning.
But physicalism is not the only direction monism has taken. At the other extreme there is idealism, the contention that there is indeed only one real thing and that it is not the physical universe measured by physics strictly speaking, but the experiential subject-consciousness doing the measuring. This subjectivity, the “mental realm” in general is shared in the sense that we all participate, that is have our individual subjectivity, within this realm and so it is not surprising that we can compare notes as it were and recognize that some components of “the mental” are experienced by all of us accounting for the appearance of the objective world. But idealism does not satisfactorily account for our technology. It is one thing to share a mental realm and agree that a tree is a tree and a rock a rock, but it is quite another to expect to use that contingent agreement to make an airplane that flies or build a functioning quantum computer.
Just as nihilism is a nonsensical corollary of physicalism, the notion that airplanes only appear to fly because we all agree that they do is nonsensical. Airplanes do not merely appear to fly they actually fly. That means the physics underlying their flight is not merely a matter of inter-subjective agreement but a necessarily true antecedent to that agreement. Physical reality must in fact be real prior to and apart from the mental. Because monism, taken seriously, permits only a single category, there is not much room between physicalism and idealism for any other strict monism. But a less strict version appears as a component of “property dualism”.
Like monism, dualisms come in various flavors. What they have in common is an acceptance of the subjective experience, and in particular free will, at face value. The physical realm is real, the mental realm is real, and beyond this, physics alone cannot account for the mental realm unless there is more to physics than has yet been observed. What this more consists in is mostly where the property dualism debate lies. On one extreme there is no more strictly speaking, but it is nevertheless asserted that a causally closed physics, a physics that comes only from physical causes and has only physical effects, can nevertheless cause a non-physical phenomenon to emerge, and is subsequently responsive, causally, to this entity. Of course this amounts to a contradiction, a physics that has only physical effects has (or causes), at least one, non-physical effect (or emergence) that being consciousness. It does however at least underpin our intuition that the mental does have reciprocal impact on the physical; our experience of free will.
Physics is the source of the mental and therefore the mental can interact with and affect physics. This all comes out very neat and tidy until one realizes that no physicist anywhere has ever detected (measured) or observed the physical eventuating the non-physical. Causal closure does not, to 300+ years of experimentation and observation, ever appear to result in anything non-physical. One is tempted to exclaim that consciousness is indeed the only such example there is, but surely this then begs the question.
To avoid such question begging, some philosophers (but understandably no physicists) have suggested that there is something hidden in physics, that is hidden in causal closure, that remains undiscovered and is specifically directed at producing subjective consciousness. One problem with this is that like subjective experience itself, these hidden properties are not measureable with physical instruments. They are merely presumed to be present because, after all, consciousness exists and there is nothing in the measureable properties of the physical that appears able to explain it. This really is more “begging the question” based on a non-negotiable faith in physicalism, but faith is indeed the right word to use here.
Philosophers have suggested several variations on these “hidden properties”. Anomalous monism (Davidson and Nagel) lies at one extreme; un-measurable properties truly hidden either in physical law (process) or the properties of objects as we otherwise know them. Their redundancy as concerns physics strictly speaking should be enough to dismiss their presence. On the other side we have those like David Chalmers who suggest instead a set of parallel laws, not strictly in physics but present (pervading the universe) along side it. This approach avoids the issue of redundancy because these parallel laws become noticible only after the emergence of observers who notice them indirectly by having a subjective experience. That is, the measure of their presence is their detection by the phenomenon of subjective experience. This idea leads directly to some form of panpsychism whose effect, prior to the emergence of consciousness, must have driven otherwise contingent physical outcomes towards life and ultimately consciousness.
This is not an entirely unreasonable hypothesis, but its problem is again the nature of the physical. There is nothing we are aware of in the phenomenon of the big bang or anywhere in physics that would serve to support either the reality or the efficacy of a parallel set of psychotropic laws. We may not know why the big bang occured, but at least there is the manifestly unstable quantum vacuum. The quantum vacuum can be manipulated (mathematically modeled) to generate all of our physics, but not anything of panpsychism.
It is exactly the fact that there appears to be nothing in physics that supports panpsychism that leads away from property dualism where the dual-reality must have its ground in physics to substance dualism in which the ground of the mental purportedly originates, reasonably enough, outside of physics. The “psychotropic laws”, after all, stand in exactly the same relation to consciousness no matter where they originate. If they cannot come from physics perhaps they originate in something else? But what? An external origin relieves physics of incompleteness at the cost of suggesting some other quality of the universe that is not only non-material (and as such capable of grounding psychotropic laws) but must have the power to interact with physics to produce all of what the mental, to common experience, appears to produce; including free will.
It is for this reason that substance dualism is so often associated with theism or deism. Although these solutions do not explain the mechanism of the interaction, they posit an entity, a God, who knows the trick. We further ascribe self-cause to that entity to block an otherwise infinite recursion of metaphysical antecedents. Personally I do not find a theistic solution to the ultimate question unreasonable. It is certainly coherent, and as concerns an “inference to a best explanation”, a legitimate limiting test recognized as generally valid where more rigorous inductive or even deductive proofs are not applicable, theism is complete. That is to say that beginning with a few assumptions as concerns the nature God must have to be an explanation or an answer to the ultimate “what must be true” question, one can show that the corollaries of these assumptions are both consistent with physics, and all of experience including qualia, intensionality, intellection in its broadest sense, and free will.
In particular theism can account, in the sense of providing explanations, for the juxtaposition in the universe of purposeless mechanism (what physics probes) and purposeful free will (the choice of the physicist to probe it), something that materialism has been singularly unable to do. I have written three books exploring the theistic inference to best explanation of human experience and more recently “Prolegomena to a Future Theology” laying out a minimal and consistent set of axioms from which the rest can be derived. I will not further explore this subject here. In part II I will explore what philosophers, and physicists being philosophers, have proposed as explanation for why the physical universe is the way it is even leaving consciousness aside. All of these suggestions are made assuming that theism is not true, that no God exists. Yet while remaining anchored ostensibly in the physical all of these hypotheses suffer from the same problems as metaphysics in general and theism in particular as concerns physics; among them underdetermination and redundancy.