I shall now come to the argument, which may be briefly stated.
The design is to shew, that those who have once professed the true faith of Christ, ought to respond to their calling to the last. After having then extolled, in high terms, the grace of God, he recommends to them holiness of life, because God usually punishes in hypocrites a false profession of his name, with dreadful blindness, and on the other hand he increases his gifts to those who truly and from the heart embrace the doctrine of religion. He, therefore, exhorts them to prove their calling by a holy life. And, to give a greater weight to his admonitions, he says that he is already near his end, and at the same time, excuses himself that he so often repeated the same things, his object being that they who should remain alive on the earth after his death, might have what he, when alive, wrote, more deeply fixed in their minds.
And as the foundation of true religion is the certainty or the truth of the gospel, he shews, first, how indubitable is its truth by this fact, -- that he himself had been an eyewitness of all things which it contains, and especially that he had heard Christ proclaimed from heaven to be the Son of God; and, in the second place, it was God's will that it should be borne witness to, and approved by the oracles of the prophets.
He, however, predicts, at the same time, that danger was approaching from false teachers, who would spread impious inventions, as well as from the despisers of God, who would mock all religion; and he did this, that the faithful might learn to be watchful, and that they might be fortified. And he seems to have spoken thus designedly, lest they expected that the course of truth in the kingdom of Christ would be tranquil and peaceable, and free from all contention. He afterwards, as on a tablet, describes the character and manners of those who would, by their corruptions, pollute Christianity. But the description which he presents, especially suits the present age, as it will be more evident by a comparison. For he especially draws his pen against Lucianic men, who abandon themselves to every wickedness, and take a profane license to shew contempt to God, yea, and treat with ridicule the hope of a better life; and at this day we see that the world is everywhere full of such rabble.
He further exhorts the faithful, not only to look always for the coming of Christ with suspended and expectant minds, but also to regard that day as present before their eyes, and in the meantime to keep themselves unpolluted for the Lord: in which doctrine he makes Paul as his associate and approver; and to defend his writings from the calumnies of the ungodly, he severely reproves all those who pervert them.