The doctrine of post-baptismal sin, especially when realized in the doctrine of Purgatory, leads the inquirer to fresh developments beyond itself. Its effect is to convert a Scripture statement, which might seem only of temporary application, into a universal and perpetual truth. When St. Paul and St. Barnabas would “confirm the souls of the disciples,” they taught them “that we must through much tribulation enter into the kingdom of God.” It is obvious what very practical results would follow on such an announcement, in the instance of those who simply accepted the Apostolic decision; and in like manner a conviction that sin must have its punishment, here or hereafter, and that we all must suffer, how overpowering will be its effect, what a new light does it cast on the history of the soul, what a change does it make in our judgment of the external world, what a reversal of our natural wishes and aims for the future! Is a doctrine conceivable which would so elevate the mind above this present state, and teach it so successfully to dare difficult things, and to be reckless of danger and pain? He who believes that suffer he must, and that delayed punishment may be the greater, will be above the world, will admire nothing, fear nothing, desire nothing. He has within his breast a source of greatness, self-denial, heroism. This is the secret spring of strenuous efforts and persevering toil, of the sacrifice of fortune, friends, ease, reputation, happiness. There is, it is true, a higher class of motives which will be felt by the Saint; who will do from love what all Christians, who act acceptably, do from faith. And, moreover, the ordinary measures of charity which Christians possess, suffice for securing such respectable attention to religious duties as the routine necessities of the Church require. But if we would raise an army of devoted men to resist the world, to oppose sin and error, to relieve misery, or to propagate the truth, we must be provided with motives which keenly affect the many. Christian love is too rare a gift, philanthropy is too weak a material, for the occasion. Nor is there an influence to be found to suit our purpose, besides this solemn conviction, which arises out of the very rudiments of Christian theology, and is taught by its most ancient masters,—this sense of the awfulness of post-baptismal sin. It is in vain to look out for missionaries for China or Africa, or evangelists for our great towns, or Christian attendants on the sick, or teachers of the ignorant, on such a scale of numbers as the need requires, without the doctrine of Purgatory. For thus the sins of youth are turned to account by the profitable penance of manhood; and terrors, which the philosopher scorns in the individual, become the benefactors and earn the gratitude of nations.  – from On the Development of Doctrine (1845)