2. In principle and in fact, materialism radically excludes the presence and action of God, who is spirit, in the world and above all in man. Fundamentally this is because it does not accept God's existence, being a system that is essentially and systematically atheistic. This is the striking phenomenon of our time: atheism, to which the Second Vatican Council devoted some significant pages. Even though it is not possible to speak of atheism in a univocal way or to limit it exclusively to the philosophy of materialism, since there exist numerous forms of atheism and the word is perhaps often used in a wrong sense, nevertheless it is certain that a true and proper materialism, understood as a theory which explains reality and accepted as the key-principle of personal and social action, is characteristically atheistic. The order of values and the aims of action which it describes are strictly bound to a reading of the whole of reality as "matter." Though it sometimes also speaks of the "spirit" and of "questions of the spirit," as for example in the fields of culture or morality, it does so only insofar as it considers certain facts as derived from matter (epiphenomena), since according to this system matter is the one and only form of being. It follows, according to this interpretation, that religion can only be understood as a kind of "idealistic illusion," to be fought with the most suitable means and methods according to circumstances of time and place, in order to eliminate it from society and from man's very heart. (Papal Encyclical, Dominum et Vivificantem, 18 May 1986).
3. An error of modernism identify by the belief that: No other forces are to be recognized except those which reside in matter, and all the rectitude and excellence of morality ought to be placed in the accumulation and increase of riches by every possible means, and the gratification of pleasure. (Papal Encyclical, Quanto Conficiamur, 10 August 1863).