I have just noticed something about the fifth petition of the Lord's Prayer.
Forgive us our trespasses, as we forgive those who trespass against us.
I'd always thought of the "as we forgive those" as something like a parenthetical reminder or doctrinal footnote, a short way of saying that the party of the first part acknowledges that the Party of the second part shall deem Himself free of all obligations in re. this petition in the event that the party of the first part fails to forgive those who trespass against the party of the first part.
But while it's true that we will be forgiven as we forgive, the statement isn't a doctrinal assertion, it's a petition. Every time we say an "Our Father," we are asking God to forgive us as we forgive others. We are declaring, "It is my will that, as I forgive, so shall I be forgiven."
We aren't simply acknowledging that forgiveness is transitive; we are praying for it to be transitive. Which is a brash thing to do if we aren't actually planning on doing much forgiving.
But you may think, "I shall say what goes first in the petition, namely, 'forgive us,' but that 'As we forgive those who trespass against us,' I shall not say." Would you seek to deceive Christ? You certainly do not deceive Him. For Christ who made this prayer remembers it well, and cannot be deceived. If therefore, you say it with the lips, let the heart fulfill it.
That's good advice, certainly, but what of the one who won't follow it?
But one may ask whether he who does not intend to forgive his neighbor ought to say: "As we forgive those who trespass against us." It seems not, for such is a lie. But actually it must be said that he does not lie, because he prays not in his own person, but in that of the Church which is not deceived, and, therefore the petition itself is in the plural number.
Finally, St. Thomas proposes two forms of forgiveness:
This doesn't mean that only some few people, specially picked by God, have to forgive perfectly, while most of us are only called to a second-rate forgiveness.
Rather, St. Thomas is saying that even the stubborn fellow who does not intend to forgive his neighbor is perfectly capable of forgiving him anyway when his neighbor asks for forgiveness. It's not perfect, but it's a start, and enough of a one that whoever is prepared to make it isn't lying when he prays this petition.