Material Substance

a kind of matter which, in contrast to a physical force field, possesses a rest mass.

In the final analysis, substance is composed of elementary particles whose rest mass is not equal to zero. (It is basically made up of electrons, protons, and neutrons.) In classical physics, substance and a force field are represented as having two kinds of absolutely opposed matter; the first of these was said to have a discrete structure and the second to be continuous. In quantum physics, which introduced the idea of the dualistic, corpuscular-wave nature of any micro-object, the two kinds of matter are no longer viewed as opposites. The discovery of the close relation between substance and a force field led to more profound concepts concerning the structure of matter; on this basis the categories of matter and material substance were rigorously separated. For many centuries these categories had been considered identical in philosophy and science; moreover, the philosophical meaning remained for the category of matter, whereas the concept of material substance retained its scientific meaning in physics and chemistry. Under conditions prevailing on earth, material substance is encountered in four states: gas, liquid, solid, and plasma. The proposition has also been stated that material substance also exists in a unique hypersolid state (for example, in neutron stars).