All that exists is matter and energy, mysterious, infinitely complex, divine. Region of starbirth in the nebula NGC 604, part of the M33 galaxy in Triangulum constellation. Hui Yang and NASA, Hubble Space Telescope, January 17, 1995. Philosophical materialism has nothing to do with materialism in the sense of consumerism or the desire to amass material possessions.
Philosophical materialism means simply the belief that everything that exists is matter.
Everything has a material explanation. Mysterious unidentified spiritual forces are no more an explanation than are aliens or gods. Of course an open-minded science would never assert that we already know all forms of matter and energy. In fact modern science predicts several kinds of particles which have not yet been directly observed. Some theories of the origin of the universe predict an entire class of dark matter.