7 There is no doubt then that, as this instance proves, the undutiful (or ungodly) must be distinguished from the sinner. And, indeed, general opinion agrees to call those men ungodly who scorn to search for the knowledge of God, who in their irreverent mind take for granted that there is no Creator of the world, who assert that it arrived at the order and beauty which we see by chance movements, who, in order to deprive their Creator of all power to pass judgment on a life lived rightly or in sin, will have it that man comes into being and passes out of it again by the simple operation of a law of nature.
Thus, all the counsel of these men is wavering, unsteady, and vague, and wanders about in the same familiar paths and over the same familiar ground, never finding a resting-place, for it fails to reach any definite decision. They have never in their system risen to the doctrine of a Creator of the world, for instead of answering our questions as to the cause, beginning, and duration of the world, whether the world is for man, or man for the world, the reason of death, its extent and nature, they press in ceaseless motion round the circle of this godless argument and find no rest in these imaginings.
Source: Homilies on the Psalms (New Advent)