PW: You've written books on the sacraments of reconciliation (Lord, Have Mercy) and Eucharist (The Lamb's Supper). Why a book on all seven sacraments?

This book [Swear to God] in a certain sense I want to call "a magnum opus." It isn't written for academics, but on the other hand, it is an attempt to pull together some of the big ideas I found to be the most exciting and the most illuminating in terms of what God was doing when he fashioned creation—how he did it and what he was doing as he continued making covenants down through the ages.

Is this a book for Catholics or Protestants, or both?

I definitely write more for Catholics because I feel like an immigrant who has come into a country where there are a lot of natives who don't necessarily appreciate fully all they were born into. Sometimes it takes an immigrant to explain to the natives all they have around them. While I hope that Protestants would read it—and I think they would really be pleased with what they found—I think the principal audience is my fellow Catholics who live their lives from cradle to grave celebrating the sacraments. Everybody knows [sacraments] are important. Everybody believes they have power. But what is the origin of the power, and why is it that these things are not mere rituals?

What does your background as an evangelical Protestant bring to your writing about Catholicism?

The Bible is the lingua franca for evangelicals and I immersed myself in scripture for many years, going through it and finding that the language and logic of scripture made so much sense out of life. I had a certain biblical fluency, so what I want to do is help impart biblical literacy to Catholic laypeople. The Bible is the only thing that has to be read at Mass, and the Mass is the only thing Catholics have to attend every week.

Have you been welcomed by Catholics or have some been suspicious of you?

I must say I've been astounded by the sense of homecoming and warmth of reception, because I really did feel like I was coming in out of the cold—[I had been] anti-Catholic, and [was] profoundly sorry for trying to get Catholics to leave the church. I never expected to have cardinals, archbishops and Catholic biblical scholars thanking me for my work.

What about the sacraments today? Are they out of favor or on the verge of revival?

I would say they're on the verge of revival, especially the most blessed sacrament. I feel there is a renewal of eucharistic devotion, not just in individual piety, but in the public. It's the idea that when we go to Mass, we are surrounded by angels and saints. I would also say that the sacrament of confession has made a dramatic comeback, though it still has a way to go before it catches up to where it was on Saturday afternoons in the 1950s.

What was the biggest misconception that you hoped to correct in writing this book?

There were three things I wanted to clear up. One was the sense that these are rituals and they're boring, or merely symbolic. That to me is just empirically false. When you look at the sacraments, they are based on divine utterances; they don't just convey human life and justice, but divine life and justice. The second thing I wanted to do was to look at the notion of sacrament. This word isn't found in the Bible, nor is the Trinity and other words. But where do you find the word "covenant"? Everywhere in the Bible. The sacraments create a divine kinship between us and God, and among ourselves as well. The third thing I wanted to clear up is why there are seven sacraments. It seems somewhat arbitrary. No, it's not. God has been "sevening" himself since creation. This means there aren't just accidentally seven. Christ is bringing about his new creation through the graces of the sacraments.