The fundamental characteristic of materialism is that it starts from the objectivity of science, from the recognition of objective reality reflected by science, whereas idealism needs “detours” in order, in one way or another, to “deduce” objectivity from mind, consciousness, the “psychical”.
Sensation is an image of matter in motion. Save through sensations, we can know nothing either of the forms of matter or of the forms of motion; sensations are evoked by the action of matter in motion upon our sense-organs. That is how science views it.
“Matter disappears”, only equations remain. At a new stage of development and apparently in a new manner, we get the old Kantian idea: reason prescribes laws to nature.
Materialism and Empirio-Criticism: Critical Comments on a Reactionary Philosophy, 1908, Progress Publishers, Moscow, 1975, pp. 275, 282, 288