Old school materialism was demolished in which the world is basically made up of the substances we perceive. Instead, we find out that solid objects are mostly empty space, forces are fields acting over a distance, Relativity has counter intuitive results for time, space and mass, and QM demonstrates that matter and energy behave in spooky ways.

The material world went from something solid we could touch, see, smell, etc. to something ghostly and mathematically abstract. Scientists call it physical.

The old material world turns out to be largely an illusion of our senses and minds, replaced by physical theories. Plato's cave is inverted. The scientist wonders outside the cave of the solid objects to find ghostly forms instead.

Chomsky discusses this here:

https://www.youtube.com/watch?v=aydw2neS1W8&feature=youtu.be...