"If we ask, why penance and reparation, the first answer is: Because God wants it.
But if we press the question: Why does God want it? Then we must say, because in His mysterious wisdom, His justice requires it. We may legitimately say, without really understanding it, that He has no choice. Having given us a free will, if we abuse liberty, we must use our freedom to repay to God the love we have stolen from Him (which is penance) and repair the damage we have done (which is reparation).
Notice, all along I have been using the first person plural, "we", because penance and reparation are owed to God not only because I have individually sinned, but because we human beings have sinned and are sinning, in our day, on a scale never before conceived in the annals of history.
We know better than Cain after he killed his brother, Abel. We are our brother's keepers. We are mysteriously co-responsible for what other people do wrong. There is a profound sense in which all of us are somehow to do penance and make reparation, not only for our sinful misdeeds, but for the sins of our country and, indeed, for the sins of the whole human race.
We return to our question: Why penance and reparation? Because, in Christ's words, "Unless you do penance, you shall all likewise perish".
Is it any wonder that on Pentecost Sunday, after Peter preached his sermon, and rebuked the people for their sins, and they asked him, "what must we do," his first word to the multitude was the imperative verb, "Repent!"
Is it any wonder that Our Lady of Fatima's message to a sinful world in our day, may be summarized in the same imperative, "Do penance."
Indeed, the calamities that we have so far seen in this present century: two world wars with more casualties than in all the previous wars of history, and the threat of a nuclear holocaust that hangs over us like a tornado cloud. All of this is God's warning to do penance and reparation. Why? Because God is not mocked.
You do not offend God with impunity. You do not sin without retribution. You do not ignore the will of the Almighty and expect the Almighty to ignore what you do.
What bears emphasis, however, is that this retribution is either to be paid willingly, with our penance and reparation, or will be paid unwillingly within the divine punishment.
The divine logic is simple, awfully simple, and all we have to do is learn what God is telling us. Either we do penance and reparation because we want to, or we shall suffer (against our will) the consequences of our sins in this life, and in the life to come.
But remember, this penance and reparation is to be done not only for what we have personally done wrong. It is for all the pride and lust, for all the cruelty and greed, for all the envy and laziness and gluttony of a sin-laden human family.
God is merciful and in fact as our Holy Father has told us, Jesus Christ is the Incarnation of divine mercy. But God's mercy is conditional. It is conditional on our practice of penance and reparation."