All science is materialistic

[polymath257]

Matter and mass are not equivalent terms.

Energy would be in Joules, mass would be in kilograms and '"c squared' would be meters squared divided by seconds squared.

And in relativistic units, they would be the same.

But that isn't relevant to the comment you are replying to, which has to do with the distinction between 'matter' and 'mass'. Mass has a very definite meaning in physics, related to the rest energy of a particle. Matter has no such basic meaning, being more of a term used by chemists and concerned at a different level of organization. Some physicists label a particle 'matter' if it is a first generation fermion. So up and down quarks and electrons qualify, but photons, strange quarks, gluons, and Higg's bosons do not.

Angrboda is correct here.