“You can’t get an ‘ought’ from an ‘is.’” That’s one of the slogans of modern secular philosophy.

But it’s wrong for two reasons. First, it’s inconsistent with itself: Secular philosophy is constantly telling us what we ought to do (or not do) because of the way the world is! Second, it’s inconsistent with our faith. This week’s readings give us several examples of how “ought” follows from “is.”

We read from First Thessalonians this week, and one of the letter’s themes is that how we ought to behave is rooted in the “is” of our relationship with Jesus Christ. St. Paul says, basically: The Gentiles don’t know how they ought to behave because they don’t know who God is. But Christians, because we know who God is, and because of the gift of life we’ve received in Jesus, ought to behave differently. The indicative — what is the case — leads to an imperative: how we ought to behave.

We celebrate the memorial of the death of St. John the Baptist this week on Aug. 29. John got in hot water precisely because he grasped and proclaimed this connection, telling Herod: Herodias is your brother’s wife, therefore you ought not have her as your wife. The spirit of secular philosophy was alive in Herodias, and John was martyred for insisting on the link between is and ought.

This week we hear Jesus talking about the Kingdom of God, and His message reinforces the link: You do not know the hour when the Lord will come, therefore you ought to stay awake and be vigilant! The parable of talents, which we also hear this week, follows the same structure: We have received gifts (talents), therefore we ought to invest them in the Lord’s work. The lazy servant is precisely the one who doesn’t act on the link between is and ought!

The Office of Readings this week gives an exhortation from St. John Chrysostom. He starts by pointing out that we recognize how the Body of Christ is present to us on the altar, and we ought to give due reverence to Him there. But then he points out that it’s the same Jesus who is present to us in our neighbors in need. The exhortation follows: We ought to give Him reverence there, as well. Jesus is present in these two different modes; we ought to care for Him in each mode of His presence. If we miss the link between is and ought in either case, it’s a failure of faith.

I’m taking great pains to point out this link because I think it pertains to some of the great battles we’re facing these days. Whether it’s gun violence, the death penalty or abortion, the “is” of human dignity calls for an “ought” in our behavior and our laws. If we’re to live our faith with integrity, we need to trace those links with clarity and consistency.