Ever since at least Russell (1927), many philosophers have argued that materialism – and, I now point out, classical theism – have an “explanatory gap” problem of another sort. For science only tells us about the structure and dynamics of matter -- i.e., its extrinsic, relational properties -- and not its intrinsic properties. As D.M. Armstrong (1968) put it:
"...[I]f we look at properties of physical objects that physicists are prepared to allow them, such as mass, electric charge, or momentum, these show a distressing tendency to dissolve into relations one object has to another. What, then, are the things that have these relations to each other? Must they not have a non-relational nature if they are to sustain relations? But what is this nature? Physics does not tell us." (p. 282)
Subsequent progress in science only seems to underscore this point (cf. Ladyman and Ross 2007; Davidson 2014). Many thus now argue for ontic structural realism, according to which reality consists of relations without relata, and it is only “relations all the way down”. Unfortunately, to date, even the most strident defenders of ontic structural realism have failed to give a fully satisfying account of the view (cf. McKenzie 2017). Incoherence threatens. This is the explanatory gap problem for both conservative naturalism and theism: both views give us a physical universe with a hollow core, as neither provides the resources to provide intrinsic properties to ground its extrinsic, relational properties.
There is thus pressure to say that there must be some stock of intrinsic properties to physical reality, and yet physical reality seems to lack such properties. What is a naturalist or a theist to do? The Russellian monist answers: The only intrinsic properties we know of are phenomenal properties of subjective experience. The Russellian monist thus posits that phenomenal properties ground the relational properties of physics. Happily, then, Russellian monism appears to solve both the hard problem of consciousness and the intrinsic properties problem in one stroke. The structure-and dynamics-argument therefore offers another powerful line of support for liberal naturalism vis-a-vis theism.
 See, for example, Russell (1927), Strawson (1986), Chalmers (1996), Stoljar (2006), Pereboom (2011), Alter & Nagasawa (2012), Alter (2016) and Goff (2017).
Lewis (1986) argued that shape is an intrinsic property of material objects, but Davidson (2014) has argued persuasively that shape is relative to a given inertial reference frame.
Alter, Torin. 2016. “The Structure and Dynamics Argument Against Materialism”, Nous 50 (4): 794-815.
-----. and Yujin Nagasawa. 2015. Consciousness in the physical world: Perspectives on Russellian Monism (Oxford: Oxford University Press).
Armstrong, D.M. 1968. A Materialist Theory of Mind. New York: Routledge.
Chalmers, David. 1996. The Conscious Mind: In Search of a Fundamental Theory (Oxford: Oxford University Press).
Davidson, Matthew. 2014. “Special Relativity and the Intrinsicality of Shape”, Analysis 74 (1): 57-58.
Goff, Phillip. 2017. Consciousness and Fundamental Reality, Oxford: Oxford University Press.
Ladyman, James and Don Ross, with David Spurrett and John Collier. 2007. Every Thing Must Go: Metaphysics Naturalized, Oxford University Press.
Lewis, David. 1986. On the Plurality of Worlds. Oxford: Oxford University Press.
McKenzie, Kerry. 2017. “Ontic Structural Realism”, Philosophy Compass 12 (4): e12399.
Pereboom, Derk. 2011. Consciousness and the Prospects for Physicalism (Oxford: Oxford University Press).
Russell, Bertrand. 1927. The Analysis of Matter. London: George Allen & Unwin.
Stoljar, Daniel. 2006. Ignorance and Imagination: The Epistemic Origin of the Problem of Consciousness (Oxford: Oxford University Press).
Strawson, Galen. 2008. Real Materialism: And Other Essays (Oxford: Oxford University Press).