In this chapter, Calvin argues that Jesus is both true God and true man by appealing to the Scriptures. He dismisses the idea that even without Adam's Fall, Christ would have become man to be the head of humanity. He does so partly by arguing that such idea is a speculation that cannot be grounded in Scripture, and hence be rejected. He also shows that such idea is absurd when thinking about Christ's headship over the angels as He never "becomes" an angel to be the head. Calvin strongly opposes Osiander's view that man was fashioned according to the pattern of the Messiah to come in flesh (this was a subtle point with some significant consequences, but it was a bit hard to follow).
Calvin's view or summary of atonement is stated in section 3 as below:
"that man, who by his disobedience had become lost, should by way of remedy counter it with obedience, satisfy God's judgment, and pay the penalties for sin. Accordingly, our Lord came forth as true man and took the person and the name of Adam in order to take Adam's place in obeying the Father, to present our flesh as the price of satisfaction to God's righteous judgment, and, in the same flesh, to pay the penalty that we had deserved. In short, since neither as God alone could he feel death, nor as man alone could he overcome it, he coupled human nature with divine that to atone for sin he might submit the weakness of the one to death; and that, wrestling with death by the power of the other nature, he might win victory for us."