Calvin on I Peter 1:1

To the elect, or the elected. It may be asked, how could this be found out, for the election of God is hid, and cannot be known without the special revelation of the Spirit; and as every one is made sure of his own election by the testimony of the Spirit, so he can know nothing certain of others. To this I answer, that we are not curiously to inquire about the election of our brethren, but ought on the contrary to regard their calling, so that all who are admitted by faith into the church, are to be counted as the elect; for God thus separates them from the world, which is a sign of election. It is no objection to say that many fall away, having nothing but the semblance; for it is the judgment of charity and not of faith, when we deem all those elect in whom appears the mark of God’s adoption. And that he does not fetch their election from the hidden counsel of God, but gathers it from the effect, is evident from the context; for afterwards he connects it with the sanctification of the Spirit As far then as they proved that they were regenerated by the Spirit of God, so far did he deem them to be the elect of God, for God does not sanctify any but those whom he has previously elected.