John Calvin Commentary 2 Thessalonians 2:12

"that they all might be judged who believed not the truth, but had pleasure in unrighteousness." — 2 Thessalonians 2:12 (ASV)

That all may be condemned. This means that they may receive the punishment due for their impiety. Thus, those who perish have no just reason to argue with God, since they have obtained what they sought. For we must keep in view what is stated in Deuteronomy 13:3: that the hearts of men are subjected to trial when false doctrines spread, since these doctrines have no power except among those who do not love God with a sincere heart.

Let those, then, who take pleasure in unrighteousness reap the fruit of it. When he says all, he means that contempt of God finds no excuse in the great crowd and multitude of those who refuse to obey the gospel. God is the Judge of the whole world, so He will inflict punishment upon a hundred thousand no less than upon one individual.

The participle εὐδοκήσαντες (taking pleasure) means, so to speak, a voluntary inclination to evil. In this way, every excuse is cut off from the ungrateful when they take so much pleasure in unrighteousness, as to prefer it to the righteousness of God. For by what violence will they claim to have been driven to turn away from God in a mad rebellion—from God, to whom the guidance of nature led them? It is at least evident that they willingly and knowingly lent an ear to falsehoods.