There may be some truth (atheists) do not need to believe in a god to be good, but then if they do not believe in a god, who do they believe gives the Universal Law of following good and shunning evil? Obviously, mankind. But then that is a dangerous thing, for if a man does not believe in a god capable of giving perfect laws, he is in the position of declaring all laws come from man, and as man is imperfect, he can declare that as fallible men make imperfect laws, he can pick and choose what he wishes to follow, that which, in his own mind seems good. He does not believe in divine retribution, therefore he can also declare his own morality contrary to what the divine may decree simply because he believes there is no divine decree. He may follow his every whim and passion, declaring it to be good when it may be very evil, for he like all men is imperfect, so how can he tell what is verily good? The atheist is in danger of mistaking vice for good and consequently follow another slave master and tyrant, his own physical and mental weakness. Evil would be wittingly or unwittingly perpetrated, therefore, to recognise the existence of a perfect divine being that gives perfect Universal Laws is much better than not to believe in a god, for if there is a perfect god, they will not allow their laws to be broken with impunity as in the case with many corrupt judges on earth, but will punish accordingly in due time. Therefore, to be pious and reverent is the surest path to true freedom as a perfect god will give perfect laws to prevent all manner of slavery, tyranny and moral wantonness, even if we do not understand why they are good laws at times.
The central thesis of Surnaturel, then, is that, neither in patristic nor in medieval theology, and certainly not in Thomas Aquinas, was the hypothesis ever entertained of a purely natural destiny for human beings, something other than the supernatural and eschatological vision of God. There is only this world, the world in which our nature has been created for a supernatural destiny. Historically, there never was a graceless nature, or a world outside the Christian dispensation. This traditional conception of human nature as always destined for grace-given union with God fell apart between attempts, on the one hand, to secure the sheer gratuitousness of the economy of grace over against the naturalist anthropologies of Renaissance humanism and, on the other hand, resistance to what was perceived by Counter-Reformation Catholics as the Protestant doctrine of the total corruption of human nature by original sin. The Catholic theologians, who sought to protect the supernatural by separating it conceptually from the natural, facilitated the development of the humanism which flowered at the Enlightenment into deism, agnosticism and ultimately atheism. The conception of the autonomous individual for which the philosophers of the Age of Reason were most bitterly criticized by devout Catholics was, de Lubac suggested, invented by Catholic theologians. The philosophers which broke free of Christianity, to develop their own naturalist and deist theologies, had their roots in the anti-Protestant and anti-Renaissance Catholic Scholasticism of the late sixteenth and early seventeenth centuries.