Defining Matter
The nature and definition of matter - like other key concepts in science and philosophy - have occasioned much debate. Is there a single kind of matter (hyle) which everything is made of, or multiple kinds? Is matter a continuous substance capable of expressing multiple forms (hylomorphism), or a number of discrete, unchanging constituents (atomism)? Does it have intrinsic properties (substance theory), or is it lacking them (prima materia)?
One challenge to the traditional concept of matter as tangible "stuff" came with the rise of field physics in the 19th century. Relativity shows that matter and energy (including the spatially distributed energy of fields) are interchangeable. This enables the ontological view that energy is prima materia and matter is one of its forms. On the other hand, the Standard Model of Particle physics uses quantum field theory to describe all interactions. On this view it could be said that fields are prima materia and the energy is a property of the field.
According to the dominant cosmological model, the Lambda-CDM model, less than 5% of the universe's energy density is made up of the "matter" described by the Standard Model of Particle Physics, and the majority of the universe is composed of dark matter and dark energy - with no agreement amongst scientists about what these are made of. This obviously refutes historical materialism which held that the only things that exist are things composed of the kind of matter with which we are broadly familiar ("traditional matter") - which was anyway under great strain as noted above from relativity and quantum field theory.
With the advent of quantum physics, some scientists believed the concept of matter had merely changed, while others believed the conventional position could no longer be maintained. For instance Werner Heisenberg said "The ontology of materialism rested upon the illusion that the kind of existence, the direct 'actuality' of the world around us, can be extrapolated into the atomic range. This extrapolation, however, is impossible... atoms are not things." Likewise, some philosophers feel that these dichotomies necessitate a switch from materialism to physicalism. Others use the terms "materialism" and "physicalism" interchangeably.
The concept of matter has changed in response to new scientific discoveries. Thus materialism has no definite content independent of the particular theory of matter on which it is based. According to Noam Chomsky, any property can be considered material, if one defines matter such that it has that property.
Read more about this topic: Materialism
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