28 The present age, Venerable Brethren, by adding new errors to the doctrinal aberrations of the past, has pushed these to extremes which lead inevitably to a drift towards chaos. Before all else, it is certain that the radical and ultimate cause of the evils which We deplore in modern society is the denial and rejection of a universal norm of morality as well for individual and social life as for international relations; We mean the disregard, so common nowadays, and the forgetfulness of the natural law itself, which has its foundation in God, Almighty Creator and Father of all, supreme and absolute Lawgiver, all-wise and just Judge of human actions. When God is hated, every basis of morality is undermined; the voice of conscience is stilled or at any rate grows very faint, that voice which teaches even to the illiterate and to uncivilized tribes what is good and what is bad, what lawful, what forbidden, and makes men feel themselves responsible for their actions to a Supreme Judge.
Source: Summi Pontificatus (Vatican.va)