The doctrine of modern Communism, which is often concealed under the most seductive trappings, is in substance based on the principles of dialectical and historical materialism previously advocated by Marx, of which the theoricians of bolshevism claim to possess the only genuine interpretation. According to this doctrine there is in the world only one reality, matter, the blind forces of which evolve into plant, animal and man. Even human society is nothing but a phenomenon and form of matter, evolving in the same way. By a law of inexorable necessity and through a perpetual conflict of forces, matter moves towards the final synthesis of a classless society. In such a doctrine, as is evident, there is no room for the idea of God; there is no difference between matter and spirit, between soul and body; there is neither survival of the soul after death nor any hope in a future life. Insisting on the dialectical aspect of their materialism, the Communists claim that the conflict which carries the world towards its final synthesis can be accelerated by man. Hence they endeavor to sharpen the antagonisms which arise between the various classes of society. Thus the class struggle with its consequent violent hate and destruction takes on the aspects of a crusade for the progress of humanity. On the other hand, all other forces whatever, as long as they resist such systematic violence, must be annihilated as hostile to the human race.
Communism, moreover, strips man of his liberty, robs human personality of all its dignity, and removes all the moral restraints that check the eruptions of blind impulse. There is no recognition of any right of the individual in his relations to the collectivity; no natural right is accorded to human personality, which is a mere cog-wheel in the Communist system. In man's relations with other individuals, besides, Communists hold the principle of absolute equality, rejecting all hierarchy and divinely-constituted authority, including the authority of parents. What men call authority and subordination is derived from the community as its first and only font. Nor is the individual granted any property rights over material goods or the means of production, for inasmuch as these are the source of further wealth, their possession would give one man power over another. Precisely on this score, all forms of private property must be eradicated, for they are at the origin of all economic enslavement... For the first time in history we are witnessing a struggle, cold-blooded in purpose and mapped out to the least detail, between man and "all that is called God." Communism is by its nature anti-religious. It considers religion as "the opiate of the people" because the principles of religion which speak of a life beyond the grave dissuade the proletariat from the dream of a Soviet paradise which is of this world. (Papal Encyclical, Divini Redemptoris, 19 March 1937).