I consider myself a (metaphysical) materialist or, to use the synonymous term that is more fashionable nowadays, physicalist, and I'm familiar with the academic literature on contemporary materialism/physicalism. But in no paper or book did I find really satisfying, fully adequate definitions of the central concepts of a material/physical object and of a material/physical property. (A material/physical property certainly isn't material/physical in the same sense as a material/physical object.) Does this mean that there actually aren't any such definitions, and that materialism/physicalism is therefore a virtually vacuous doctrine?
Material/physical objects (substances) could be defined in terms of material/physical properties:
x is a material/physical object =def x has some (intrinsic) material/physical properties.
But then the big problem is how to properly define the concept of a material/physical property.
I've been trying to devise and formulate a fully adequate definition of it for several years...