19 The root reason for human dignity lies in man's call to communion with God. From the very circumstance of his origin man is already invited to converse with God. For man would not exist were he not created by Gods love and constantly preserved by it; and he cannot live fully according to truth unless he freely acknowledges that love and devotes himself to His Creator. Still, many of our contemporaries have never recognized this intimate and vital link with God, or have explicitly rejected it. Thus atheism must be accounted among the most serious problems of this age, and is deserving of closer examination. The word atheism is applied to phenomena which are quite distinct from one another. For while God is expressly denied by some, others believe that man can assert absolutely nothing about Him. Still others use such a method to scrutinize the question of God as to make it seem devoid of meaning. Many, unduly transgressing the limits of the positive sciences, contend that everything can be explained by this kind of scientific reasoning alone, or by contrast, they altogether disallow that there is any absolute truth. Some laud man so extravagantly that their faith in God lapses into a kind of anemia, though they seem more inclined to affirm man than to deny God. Again some form for themselves such a fallacious idea of God that when they repudiate this figment they are by no means rejecting the God of the Gospel. Some never get to the point of raising questions about God, since they seem to experience no religious stirrings nor do they see why they should trouble themselves about religion. Moreover, atheism results not rarely from a violent protest against the evil in this world, or from the absolute character with which certain human values are unduly invested, and which thereby already accords them the stature of God. Modern civilization itself often complicates the approach to God not for any essential reason but because it is so heavily engrossed in earthly affairs. Undeniably, those who willfully shut out God from their hearts and try to dodge religious questions are not following the dictates of their consciences, and hence are not free of blame; yet believers themselves frequently bear some responsibility for this situation. For, taken as a whole, atheism is not a spontaneous development but stems from a variety of causes, including a critical reaction against religious beliefs, and in some places against the Christian religion in particular. Hence believers can have more than a little to do with the birth of atheism. To the extent that they neglect their own training in the faith, or teach erroneous doctrine, or are deficient in their religious, moral or social life, they must be said to conceal rather than reveal the authentic face of God and religion.
Source: Gaudium et Spes (Vatican.va)