Materialism and Physicalism
The heyday of materialism was the 19th century, when it seemed to be clear that in time the universe and everything in it would be explained by one thing, the material. Materialism was the world view that the only truly existing entity was matter. All other things (particularly thinking) could be explained by recourse to material explanation. Matter thought to be tiny hard balls of solidity or extension in three dimensions. The ontology of the world, i.e.: what exists? was answered by using just one word matter.
This was the culmination of a couple of centuries of wrangling over the Cartesian mind/body problem. It was agreed that logically, only one thing can actually exist, matter won the argument over mind and philosophical materialism reigned supreme until the advent of quantum mechanics. Then materialism failed.
Quantum mechanics and subsequent physics cannot be explained with such a simplistic account of the world. A new ontology evolved which is now used as the fundamental basis for all that exists. The new ontology includes such ephemeral entities as fields, quantum particles and spacetime points. These are the new entities that physicists see as being the fundamentals of existence. For the casual observer there was no major paradigm shift. Matter could not explain everything but the new physical entities being described could. Overnight the average materialist became a physicalist and basically assumed that it was more or less the same. But a close attention to the detail and we can see that it is not.
Materialism was a clear and distinct philosophy. It defined what it believed and it was clear what it did not believe. We could say that materialism is actually a falsifiable theory and as such is a scientific theory. It believes that the fundamental stuff of the world is matter and if that is proven to be false then materialism is falsified. If more than matter is required to explain reality, then materialism is false. The clear definition of materialism was that there is one thing that exists and that one thing is matter. Nothing else exists. The ontology of materialism is thus clearly defined.
Physicalism does not have a fixed ontology in the way that materialism had. Physicists will quite happily rearrange their idea of what is needed to explain the fundamental principles of reality. They will take things out of their list and they will add things to their list. It is a work in progress. Should a physicist deide that a new entity needs adding to the list then it will be added. Should there be no need to keep something on the list, then it will be removed. Physicalism does not make any claims about what exists in the world and what does not. The list is continuously changing and being updated according to current knowledge.
Now if at some point in the course of future science physicists decide that we need to introduce the idea of angel and demon particles into the ontology of the universe, then they will. And just because the new ontology includes angels and demons, who is to say that such an inclusion refutes physicalism?
Physicalism then is no more than the claim that some future perfect science will one day be able to explain everything. But then this is true by definition; a future perfect science will explain everything that is why it is called perfect. And more importantly, physicalism does not refute the idea that mental phenomena are fundamental. Materialism denied the mental by definition, yet materialism is not enough to understand the world. Physicalism is a work in progress and without contradicting itself, could yet be forced to accommodate the mental as a fundamental entity of existence.
The philosophy of materialism then was the idea that mental phenomena do not exist in a fundamental way. The mental was a consequence of the material. Materialism does not work as an explanation of reality so it was replaced by physicalism. Yet physicalism does not perform the same crucial task that materialism once did; that of denying the fundamental existence of mind. Because physicalism is a work still in progress, it has no clear ontology, it is not a scientific or falsifiable theory in the way materialism once was. Physicalism is true, but it is true vacuously. Physicalism cannot be proven false no matter what we discover about our universe. In that sense it is no replacement for materialism and to present materialism, an abandoned theory, or physicalism, a vacuous theory, as support for any belief is to misrepresent the facts.