The methods of physics as they’ve been understood since the time of Galileo make this limitation inevitable. As philosopher of physics Roberto Torretti writes:
While Aristotelian science favored loving attention to detail, through which alone one could succeed in conceiving the real in its full concreteness, Galileo and his followers conducted their research with scissors and blinkers… The natural processes and states of affairs under study were represented by simplified models, manageable instances of definite mathematical structures. The inevitable discrepancies between the predicted behavior of such models and the observed behavior of the objects they stood for were ascribed to “perturbations” and observation errors. (, pp. 431-32)
The “scissors and blinkers” have to do with the way that Galileo and his successors ignored or cut away from their representation of the physical world anything that cannot be captured mathematically – secondary qualities (colors, sounds, etc.), teleology or final causes, moral and aesthetic value, and so on. Thus, as Torretti writes, “modern mathematical physics began in open defiance of common sense” (p. 398). Galileo expressed admiration for those who, applying this method in astronomy, had “through sheer force of intellect done such violence to their own senses as to prefer what reason told them over that which sensible experience plainly showed them to the contrary” (quoted at p. 398).
The point isn’t that this is necessarily bad. On the contrary, it made it possible for physics to become an exact science. But physics did so precisely by deliberately confining its attention to those aspects of nature susceptible of an exact mathematical treatment. This is like a student who ensures that he’ll get A’s in all his classes simply by avoiding any class he knows he’s not likely to get an A in. There may be perfectly good reasons for doing this. But it would be fallacious for such a student to conclude from his GPA that the classes he took taught him everything there is to know about the world, or everything worth knowing, so that the classes he avoided were without value. And it is no less fallacious to infer from the success of physics that there is nothing more to material reality, or at least nothing more worth knowing, than what physics has to say about it (even if a lot of people who like to think of themselves as pretty smart are guilty of this fallacy).
Moreover, to take modern physics’ mathematical description of matter to be an exhaustive description would, as it happens, more plausibly undermine materialism altogether rather than give content to it. In particular, it arguably leads to idealism. I briefly noted in Aristotle’s Revenge (at pp. 176-77) how twentieth-century physicists Eddington and James Jeans drew this conclusion. Torretti (at pp. 98-104) notes that Leibniz and Berkeley did the same.
Here’s one way to understand Leibniz’s argument (which Torretti finds in some of Leibniz’s letters). Every geometry student knows that perfect lines, perfect circles, and the like cannot be found in the world of everyday experience. Concrete empirical geometrical properties are at best mere approximations to the idealizations that exist only in thought. But the mathematical description of the material world afforded by physics is also an abstract idealization. As such, it too can exist only in thought, and not in mind-independent reality. Of course, Leibniz’s theory of monads already purports to establish that there is no mind-independent reality, so that perception no more gives us access to such a reality than physics does. The point of the argument of the letters (as I am interpreting it) is to note that the abstractions of physics cannot be said to give us a better foundation for conceiving of the physical world as mind-independent. On the contrary, qua abstractions they are even less promising candidates for mind-independence than the ordinary perceptual world is.
Berkeley adds the consideration that systems of signs, such as the mathematics in which modern physical theory is expressed, can be useful in calculations even though some of the signs do not correspond to anything. As it happens, I discussed this theme from Berkeley in . The utility of a system of signs in part derives from the conventions and rules of the system, rather than from any correspondence to the reality represented by the system. This conventional element in physics’ mathematical representation of the material world reinforces, for Berkeley, that representation’s mind-dependence.
To try to give content to materialism by identifying matter with whatever physics says about matter would, if this is right, essentially be to transform materialism into idealism – that is to say, to give up materialism for its ancient rival. To avoid this, the materialist could, of course, appeal to some philosophical theory about the nature of matter that recognized that physics tells us only part of the story. But this would be to acknowledge that materialism is, after all, itself really just one philosophical theory among others, no better supported by science than its rivals are. It would be to see through the illusion that metaphysical conclusions can be read off from the findings of modern science.
The picture of nature provided by modern physics is in fact highly indeterminate between different possible metaphysical interpretations – materialist, idealist, dualist, panpsychist, or (the correct interpretation, in my view) Aristotelian. It is (to borrow ) a hollow vessel into which metaphysical water, wine, or for that matter gasoline might be poured. But it doesn’t by itself tell us which of these to pour.
Again, see for more, or, for instant gratification, the posts linked to below.