Last time we ended with this graphic. 1 Yet, the basic interactions are mediated by something far less "solid." The basic ontology of the physical universe is the fields! And these fields are everywhere and "in contact" at every point (provided they mutually interact; more on this below.) These fields are not what one would call solid and impenetrable. Every school kid has experience with fields -- case in point, iron filings being moved about by magnetic fields! Stuff like that "spooky" magnetic field is what the physical universe is. So the universe is more spirit-like than matter-like than most believe -- more ethereal than solid.
In spite of the modern field theoretic view of the material universe, as mentioned above, proponents of material monism seem to entertain an antiquated and superficial muddle-minded notion of material causation. This is the old atomistic and mechanistic physics where causation is something similar to the collision of billiard balls -- solid things impacting solid things and recoiling along with attendant conservation laws of energy and momentum. Causal interaction through contact.2 This false perception is, no doubt, encouraged by the observations of particles -- they being viewed as tiny solid granular bodies.
Examples of such muddle-mindedness in regard to physical causation are evident in the writings of (dare I say all?) most modern atheist philosophers of mind.
In addition to Nagel, another example is Jaegwon Kim, who wrote: "For substance dualism, it is, at bottom, the extreme heterogeneity of minds and bodies that makes causal relations between them prima facie problematic." (emph. added)3 There are a lot of unwarranted assumptions and question begging in such an assertion. It certainly betrays an ignorance of modern physics. The assumption that matter itself is "homogeneous" in kind is certainly false. Matter is not homogeneous in spite of the fact that it is called matter, and it is not a pure monism in spite of being called material monism. Contra Kim and others, matter too is extremely heterogeneous. To elaborate, I return to our figure of my prior blog. This figure is supposed to be credible to the monist. But it shows two heterogeneous types of matter interacting - a photon (a massless, neutral, spin one boson) and an electron (a massive, electrically charged, spin 1/2 fermion).
The complete (omitting only gravitation) set of fields (and associated particles) is shown in the following diagram found in the Wikipedia entry on the Standard Model. The diagram shows the particle view of a quantum field. The blue lines show the interactions between the fields/particles. Fields not connected by a blue line do not interact directly; they can only interact indirectly. So in particular -- and quite amazingly -- electrons (the "e" within the lepton box) do not interact with other electrons except indirectly by an "exchange of photons." (Note: There is no blue line that loops from the electron "e" back to itself.) So much for "like stuff" interacting with "like stuff!" The only fields that have self interactions (other than gravity) are the fields with nonlinear free field equations. These are the gluons, Higgs boson, and weak bosons (indicated by the closed blue loops). One should note: all fields of QFT are "co-located;" they mutually exist at every space-time point (i.e. at every spatial location and for all time).4 Yet, amazingly, the leptonic and quark fields though everywhere co-located are oblivious of each other (note: there is no blue line between the leptons and quarks)! That is a rather embarrassing situation for the philosopher who argues for material monism. On the basis of the material monist principle, it would seem the monist should assert that all matter must interact with all other matter. The absence of direct lepton-lepton interactions (for one among others) should be a mystery to them. But such questions seem not to worry their limited epiphenomenal "minds."
[graphic from Wikipedia]So then, the material monist can no more explain or account for material interaction (and amazingly the absence of interactions between different types of matter) among the various fields than a dualist can explain mind-body interactions. The complaint of Nagel, Kim and all material monists against dualism is superficial and is yet another example of atheist special pleading.5 As the saying goes, "That which is a problem for everyone is a problem for no one." So then, the monist's reason for accepting "monism" is based on a false principle that does not support their belief.
In closing, we should note that the diagram represents the "god" of the materialist. For the atheist, this immutable and eternal complex plurality of fields is a brute fact and accounts for all of reality. That is a most fantastic and incredible belief. It claims that human autonomy, rationality and morality are mere accidental configurations of these fields. It should be obvious to all not in the grips of irrational ideology that any such "emergent" properties are determined solely by the dance of these fields. Every future (probabilistic) state of the fields is determined by the current state via partial differential equations. Equations in which the only elements are quantities describing the configurations of the fields, and nothing more enters the equations. So much for human autonomy. As Christians we know that this intricately plural and elegant unified structure of material reality is designed by God. The material creation does not account for all of reality -- it in no way accounts for the souls, spirits and minds, human rational autonomy, abstract entities and morality. These are things for which no material monist has supplied anything close to intelligible accounts. As detailed here, Nagel's attempt is superficial and fails utterly. In fact, the so called underpinnings of the material monist principles are found to be wanting philosophically and scientifically (engaging in unanalyzed question begging and special pleading).
1 For example, quantum transition amplitudes typically involve integrals in which the time of the interaction is taken to be any time from the remote past to the remote future. Usually the integration over time is specified using the mathematical fiction of negative infinity to positive infinity.↩
2 Newtonian gravity and early electromagnetic theories first introduced the rather scandalous concept of unmediated action at a distance. That concept slowly gave way to the concept of physical fields and the first steps towards modern physics. See the Wikipedia entry action at a distance.↩
3 Jaegwon Kim, Philosophy of Mind, Westview 1998, p.133.↩
4 This feature of the fields is contrary to the old concept of matter as having the property of impenetrability or that which cannot occupy the same space at the same time. In modern physics, the closest property to this idea is the Pauli exclusion principle which only applies to like fermions. Even in this case two electrons can be in the same location as long as their other properties differ (such as one being "spin up" and the other "spin down." From the Wikipedia entry: "This effect is partly responsible for the everyday observation in the macroscopic world that two solid objects cannot be in the same place at the same time." ↩
5 It is special pleading since material interactions are also mysterious. So the rejection of dualism because it is mysterious applies equally to materialism. The supposed foundation of the entire material monist philosophy is built on a fallacy.↩