p In Marxist philosophical materialism the concept “matter” is used in its broadest sense—to denote everything that exists objectively, that is, independent of our mind and reflected in our sensations. "Matter,” Lenin wrote, "is the objective reality given to us in sensation.”

p It is very important to understand this broad meaning of the concept “matter”. Most of the old, pre-Marxian materialists regarded as matter only physical bodies and the tiny particles—atoms or corpuscles—of which these bodies are composed. Democritus and Epicurus, for instance, believed that the world consisted of atoms moving about in empty space, the Void; things were merely combinations of atoms. Subsequently, physics confirmed the ancient materialists’ brilliant conjecture of the atomic structure of matter. The concept of matter as confined only to atoms, however, was an oversimplification that led to an inadequate understanding of the material world. Yet this view of matter was revived in modern times and persisted in science up to the close of the nineteenth century.

p The term “matter” as used in Marxist philosophical materialism designates objective reality in all its multiform manifestations. Matter is not only the tiny particles of which all things are composed. It is the infinite multitude of worlds in an infinite universe; the gaseous and dust clouds of the cosmos; our own solar system with its sun and planets; the earth and everything existing on it. It is, also, radiation, the physical fields that transfer the action of one body or particle to another and connect them:,electro-magnetic, nuclear and 30 gravitational fields. Everything existing outside and independent of our mind is of a material nature.

p All sciences devoted to the study of objective reality study matter, its different qualities and states.

p The physical sciences deal with the physical states of matter. Modern physics has established that the atom is a complex structure, and by no means a simple, indivisible and immutable particle, as the old atomists believed. The scientists have also established that the atoms of one element can be converted into the atoms of another element by transformation of atomic nuclei. For instance, uranium atoms placed in a nuclear reactor are converted into plutonium atoms.

p The new physical phenomena discovered in the opening years of the century (radioactivity, X-rays, etc.) proved the divisibility and highly complex structure of the atom, led to new theories of the structure of matter and demolished the old concepts of classical physics. On the ground that the atom could not be regarded as an immutable and indivisible particle of matter, many idealist philosophers and physicists who had succumbed to idealistic delusions drew the conclusion that science had refuted the materialist conception of nature. There was talk of the "disappearance of matter”. These assertions were profoundly erroneous. Marxist philosophical materialism has never committed itself to any one-sided theory of the structure of matter, and has never sought to reduce matter to some set of unchangeable "bricks of the universe”. It has always understood matter to mean one thing and one thing only, namely, objective reality existing outside the human mind and reflected in it. Materialism and idealism hold opposite views on the source of knowledge, on the relation of consciousness to the external world. Materialism teaches that the world exists objectively, and that consciousness is a reflection of the world. The philosophical concept of matter is used to designate the entire objective world. As for the physical structure of the world and its physical properties, these are studied by physics, and as science develops our views on the physical structure of matter change. But those changes, however great, cannot shake the proposition of philosophical materialism that there exists an objective world and that physics, like many other sciences, deals with this objective, material world. "For the sole ‘property’ of matter with whose recognition philosophical materialism is bound up,” Lenin wrote, "is the property of being an objective reality, of existing outside our mind."’

p That understanding of matter is the only correct one. It embraces all the diversity of the material world, without however reducing it to any one form of matter. He who is guided by this Marxist conception will not be misled by the idealist philosophers who assert that the new discoveries in physics are proof of the disappearance of matter.

p Matter is uncreatable and indestructible. It is eternally changing, but not a single particle can be reduced to nothingness by any physical, chemical or other processes.

p Science provides ample corroboration of this thesis of philosophical materialism. Let us cite one example. Modern physics has established that, under definite conditions, such material particles as the positron and electron disappear to produce quanta (portions) of light, photons. Some physicists call this phenomenon the "annihilation of matter" which literally means complete destruction, transformation into nothingness. Idealist philosophers point to this phenomenon as a fresh “proof” of the disappearance of matter. Actually, there is no disappearance: conversion of positrons and electrons into photons is the transition of matter from one state to another, from a solid body to light. Nature knows also the reverse process—conversion of photons into positrons and electrons, that is, the conversion of light into solid matter. All these transformations conform to the law of conservation of mass and energy.

p The world presents a picture of great diversity: inorganic nature, organic nature, physical phenomena, chemical processes, plant and animal life, social life. Science and materialist philosophy reveal the unity within this diversity. This unity consists in the fact that all these infinitely diverse processes and phenomena are different states of matter, its different properties and manifestations. Engels said: "The real unity of the world consists in its materiality."^^4^^ It consists also in the fact that consciousness belongs to the same material world in which we live, and not to some other world of the hereafter, that consciousness is a property of matter organised in a special way.

The conviction of the unity of the material world was formed and strengthened in battle against the religious doctrine that divides the world into Earth and Heaven; in battle against dualism, which regards spirit and body, mind and matter, as separate and unconnected entities; in battle against philosophical idealism, which seea the unity of the world in its being a product of mind, of spirit.