Mathematics has a mysterious subject-matter, e.g. what is 1 + 1 = 2? Presumably it is a non-empirical fact. Furthermore, what is 1? Well, paradigmatically we ourselves are ones, as everyone knows (equally incontrovertibly). So the “mysterious subject” of this post will be oneself. In particular it is mysterious to me why materialism has been so popular, in modern philosophy. So for the sake of argument, suppose that we (or if that is too implausible, that aliens in the distant future) have a materialistic theory that explains everything about the world (as observed by scientists) in terms of fundamental physics.
...... When you drink a cup of coffee, for example, all those physical movements and all of the chemical reactions involved in that action are, let us say, accommodated by our theory. What could not be accommodated, of course, is the fact that there are such (scientific) observations, rather than merely (mechanical) interactions; that you taste the coffee, having chosen to drink it, and then feel its warmth in your guts. Even if all the functioning of the brain had been accommodated by our theory, and even if it also included a plausible story of how such structures could evolve by natural selection, nonetheless where and how, in our theory, would our awareness of the world arise?
...... Presumably if such a purely material world is possible, sensory organs could evolve within it (whatever innumerate ID people believe). And I’m sure that biochemical structures could be selected for behaving (e.g. for computing neurologically) as though they were individual subjects, with social consciences, and religious beliefs etc. But why would such structures also be subjects (i.e. individual beings with subjective experiences)? Why would they need to be individual subjects as well as (fuzzy) collections of objects? Not in order to enhance their fitness if, as our theory says, all their behaviour could be explained in terms of what their neurones do, and thence what the underlying particles do. But furthermore how could such an option be available in the first place, to be selected for?
...... Yet our minds certainly exist, as every scientist (and non-scientist) knows in an incontrovertibly direct way. Hypothetically our theory explains everything that our minds do, insofar as those things might be observed and spoken of, but our theory says nothing about the bare subjectivity that (as we know more directly) underlies them. So the question arises, what in the world could not be associated with something of the sort of (superficial and ineffective) subjectivity that remains unexplained by our theory? Would plants have, not minds, and perhaps not even perceptions (as we have them), but something like primitive individual sensations or feelings? Would amoebae? Maybe not, but since our brains are composed of interacting neurones (which presumably also lack minds like ours) why should a forest, for example, not have something akin to a mind? Are we really sure that there is nothing that it is like to be a forest (or a plant, a cell, an electron, a fact, a language, etc.)?
...... In other words, if our feelings of choosing to drink coffee, for example, are only a superficial companion to biochemical processes in our brains, then why should some of the biochemical processes within such ecosystems as forests (or indeed, whole biospheres) not be similarly accompanied by subjective feelings of choosing to do whatever occurs? Indeed, why would something akin to our own (directly known) subjectivity not be associated with everything and (such subjectivity being superficial and ineffective) every subset of everything? Although we naturally draw some sort of line at the brain, considering subjects to be absent beneath it, the problem is that no objective line will be indicated by our theory. That is a problem because there clearly exists one especially complex and well-defined physical individual, i.e. this Universe.
...... Now there may well be other problems with our theory saying nothing about subjectivity itself, e.g. if primitive subjectivity is associated with every subset of everything then surely telepathic communication would have been naturally selected to be a lot more common that it appears to be! But anyway, even if we were to consider subjectivity to be absent beneath the level of, say, the brain, still our theory does not make it implausible (and indeed, it actually indicates) that there would be, above that line, something that was (to put it analogically) to us much as we are to our neurones—something that may well know itself to be choosing all that occurs (much as we choose to have a cup of coffee, only more so), which would be everywhere (much as we are where our brains are), and which might even know everything (since we know so little, while our neurones know nothing), and so forth.
...... In short, materialism seems to amount to an unjustified belief about God. It would be unjustified because we could have had no scientific reason for supposing that our hypothetical theory could even amount to our most realistic theory of subjectivity, let alone God. Quite the converse, if the questions above are any indication. And it would seem to be about God because surely a more agnostic theory (one that did not equate the immaterial with nothingness) could have accommodated no less tidily the same physical observations. The difference would therefore appear to lie entirely in what those two theories imply about the subjectivity of the Universe as a whole; and note that ‘God’ was indeed the right word to use for that, despite its other connotations (or rather because of the wide variety of them). Analogously, what you drink out of is clearly a cup even if your concept of a cup requires it to be a classical object in Euclidean space while the object being drunk from is a fuzzy set of wavefunctions in more than three relativistic dimensions.
...... Anyway, if the motivations of materialism and of atheism are sufficiently akin, then our materialistic theory of everything is essentially incoherent. Of course thus far I have presented only an intuition-pump, rather than an actual argument, so note that the underlying problem here is not the incompatibility of materialism and atheism, after all (the idea that this Universe has a Creator of some sort is slightly more sensible once we are dualists, with the need to explain the origin of immaterial minds, which would clearly be more than mere subjectivities if they existed). No, the basic problem for the materialist is to explain how some sort of structure, of some sort of material objects, could have such properties as would amount to the subjectivity of an individual subject. Prima facie either no such structure could, or else all of them would, whence it is quite mysterious to me, the popularity of materialism (of either the reductive or the supervenient kind) in the absence of such an explanation. After all, the human brain not being the physical origin of so much as the physical medium for the human mind means that we could, whilst retaining all our interest in the former mechanism, also retain such hopeful (and therefore helpful) probabilities as some objective meaning to life, beyond life itself, and our personal survival beyond this life.