CHAPTER XVI. Problems About Heavenly and Earthly Divisions of the Church
60. It is more important to be able to discern and tell when Satan transforms himself as an angel of light, lest by this deception he should seduce us into harmful acts. For, when he deceives the corporeal senses, and does not thereby turn the mind from that true and right judgment by which one leads the life of faith, there is no danger to religion. Or if, feigning himself to be good, he does or says things that would fit the character of the good angels, even if then we believe him good, the error is neither dangerous nor fatal to the Christian faith. But when, by these alien wiles, he begins to lead us into his own ways, then great vigilance is required to recognize him and not follow after. But how few men are there who are able to avoid his deadly stratagems, unless God guides and preserves them! Yet the very difficulty of this business is useful in this respect: it shows that no man should rest his hopes in himself, nor one man in another, but all who are God's should cast their hopes on him. And that this latter is obviously the best course for us no pious man would deny.
61. This part of the Church, therefore, which is composed of the holy angels and powers of God will become known to us as it really is only when, at the end of the age, we are joined to it, to possess, together with it, eternal bliss. But the other part which, separated from this heavenly company, wanders through the earth is better known to us because we are in it, and because it is composed of men like ourselves. This is the part that has been redeemed from all sin by the blood of the sinless Mediator, and its cry is: "If God be for us, who is against us? He that spared not his own Son, but delivered him up for us all. . . ."  Now Christ did not die for the angels. But still, what was done for man by his death for man's redemption and his deliverance from evil was done for the angels also, because by it the enmity caused by sin between men and the angels is removed and friendship restored. Moreover, this redemption of mankind serves to repair the ruins left by the angelic apostasy.
62. Of course, the holy angels, taught by God-in the eternal contemplation of whose truth they are blessed-know how many of the human race are required to fill up the full census of that commonwealth. This is why the apostle says "that all things are restored to unity in Christ, both those in heaven and those on the earth in him."  The part in heaven is indeed restored when the number lost from the angelic apostasy are replaced from the ranks of mankind. The part on earth is restored when those men predestined to eternal life are redeemed from the old state of corruption.
Thus by the single sacrifice, of which the many victims of the law were only shadows, the heavenly part is set at peace with the earthly part and the earthly reconciled to the heavenly. Wherefore, as the same apostle says: "For it pleased God that all plenitude of being should dwell in him and by him to reconcile all things to himself, making peace with them by the blood of his cross, whether those things on earth or those in heaven." 
63. This peace, as it is written, "passes all understanding." It cannot be known by us until we have entered into it. For how is the heavenly realm set at peace, save together with us; that is, by concord with us? For in that realm there is always peace, both among the whole company of rational creatures and between them and their Creator. This is the peace that, as it is said, "passes all understanding." But obviously this means our understanding, not that of those who always see the Father's face. For no matter how great our understanding may be, "we know in part, and we see in a glass darkly."  But when we shall have become "equal to God's angels,"  then, even as they do, "we shall see face to face."  And we shall then have as great amity toward them as they have toward us; for we shall come to love them as much as we are loved by them.
In this way their peace will become known to us, since ours will be like theirs in kind and measure-nor will it then surpass our understanding. But the peace of God, which is there, will still doubtless surpass our understanding and theirs as well. For, of course, in so far as a rational creature is blessed, this blessedness comes, not from himself, but from God. Hence, it follows that it is better to interpret the passage, "The peace of God which passes all understanding," so that from the word "all" not even the understanding of the holy angels should be excepted. Only God's understanding is excepted; for, of course, his peace does not surpass his own understanding.