Susan Jacoby was on Fresh Air yesterday. She’s written a new book about the history of religious conversion. It was an interesting conversation.

GROSS: Islam and Christianity have long histories of conversion. Judaism doesn’t. It’s a religion where you’re born into it. And conversion to Judaism, I think it’s really only in modern times that that’s even been accepted, and I’m not sure it’s still accepted by all branches of Judaism.

JACOBY: No, Terry. I’m going to correct you on that. People think that, that conversion to Judaism is just a modern phenomenon. But there was an era in the late Roman Empire Judaism was not a proselytizing religion. It didn’t go out looking for converts, but it accepted converts. And one of the interesting things is is that Judaism was very attractive to the Roman aristocracy. Now most of the conversions that actually occurred were probably the result of mixed marriages of Roman women marrying into Jewish families. But it isn’t true that there weren’t conversions to Judaism then. As I said, they didn’t proselytize, but they accepted and in that respect, not so different from conversions to Judaism resulting from mixed marriages today. The Roman Empire was fairly tolerant of religious choice as long as you made a point not of thumbing your nose in public at the Roman gods.

GROSS: So why was conversion accepted then but not after?

JACOBY: Well, very simple, the Christian church became ascendant in the Roman Empire. The Roman emperors became Christians. Constantine was the first, of course, but soon afterwards. And once the Roman Catholic Church in the West became the church most closely connected with the state, the Roman Catholic Church did not recognize the validity of any religion other than its own. So that it was not only Jews were a thorn in their side because Jews in general refuse to convert, but pagans converted and masked to Christianity. It was the thing to do. If you were ambitious, if you wanted to get along, that’s what happened, not so different from anything else. But the short answer is that the Christian religion did not tolerate heresy.

And you know what, kids? That’s still true today! The Roman Catholic Church does not recognize the validity of any religion other than its own. It pretends to, sort of, at times, for the sake of interfaith conferences and politeness when foreign visitors come knocking, but other than that it simply tells us what’s what.

Jacoby’s father was a non-practicing Jew but he converted to Catholicism after he married her Catholic mother.

GROSS: Funny thing, though, your father ended up being a gambler – having a gambling problem.

JACOBY: Well, my grandfather didn’t know that (laughter) at the time. And indeed my father – one of the reasons for his conversion was he had a terrible gambling problem, and my mother was going to leave him if he didn’t get control of it. He thought since he knew nothing about Judaism – he’d been brought up in a completely nonreligious Jewish home – he thought just practicing a religion might help him overcome his gambling problem.

And this too is a theme in so many conversions, whether it’s alcoholism or gambling, the desire to overcome some personal fault which the person feels he or she cannot do on his or her own. Look, President George W. Bush is a born-again Christian, which I do consider a conversion, and I should say that I define a true conversion as any conversion that requires a real change in the way someone lives.

And so my father’s conversion was sincere, even though he didn’t believe all of the technical points of Catholic doctrine, just as I’m sure George W. Bush’s conversion helped him overcome his problems with drink. And this is a theme in so many conversions that just transcends any individual or any family.

The conversation moves to something else for a time and then returns to that.

GROSS: You know how you said your father converted primarily because he wanted to give up his gambling problem and he knew if he didn’t he’d basically lose his family…

JACOBY: Yes.

GROSS: …And so he needed help and he thought, you know, converting to Catholicism would help him. And, as you point out, that’s a reason why a lot of people convert because they need – they need to feel that there’s a power greater than themselves that can guide them and help them and also that there’s, like, a discipline that will help them.

JACOBY: Yes.

GROSS: Did it help him? Did the conversion help him give up gambling?

JACOBY: I think it did. I actually think it did. For one thing, the Catholic Church in particular has this one thing – confession – in which you could go, confess to a priest and obtain absolution of your sins. And there was a routine and a ritual and I think – I think that it did help him, yes.

GROSS: And did that affect your view of faith when you found that out?

JACOBY: No. I’d be the last person in the world to deny that there are many people for whom faith is – can be a great sustaining force. You know, people often wrongly think that atheists want to convert other people to atheism (laughter). I am completely uninterested in that. And atheism, by the way, is not a religion. One of the things, in fact, that atheism lacks are the kinds of rituals that religion does provide and I would be the first to say that.

I don’t, for example, ever participate in debates about the existence or nonexistence of God because I can’t imagine why anyone would be persuaded one way or the other by such things. And so I don’t deny that religion is very healthful* to a lot of people. And as long as they don’t try to convert me, I have, you know, nothing – and to interfere with the rights of people to believe other religions or to not believe in any religion at all – as long as they mind their own religion – perfectly all right with me, in the case of my father, as well as any other religious convert I know.

*I think she either said or meant to say “helpful” not “healthful.”

As for what she says – I know what she means, but at the same time, I’m always curious about how people manage to believe the beliefs. And I’m interested enough in converting people to want to make atheism at least more visible and available – and more acceptable. But sitting people down and trying to argue them out of religion? No, I’m not into that either.

GROSS: This is FRESH AIR. I’m Terry Gross back with Susan Jacoby, author of the new book, “Strange Gods: A Secular History Of Conversion.” One of her earlier books is a memoir about the history of religious conversions in three generations of her own family. Jacoby is also the author of “A History Of American Secularism.” She describes herself as an atheist.

You wrote a recent op-ed in The New York Times that was headlined, “Sick And Tired Of God Bless America,” and this was about how you were tired of hearing political speeches end with God Bless America. What’s your problem with that?

JACOBY: They didn’t used to, you know. God Bless America started to become an almost ritualistic incantation at the end of political speeches really with Ronald Reagan. It appears occasionally before, but it was not that common. And of course since it was a song that wasn’t written by Irving Berlin until the 20th century (laughter), none of the 19th century presidents said God Bless America at the end of speeches, either. I think that the symbolism which suggests that everybody is religious and that even presidents who believe in church and state feel obliged to do this…

GROSS: Believe in the separation of church and state.

JACOBY: Who believe in the separation of church and state feel obliged to do this. And not only, some presidents are more careful than others to make it an inclusive God, but there is also plain talk about Jesus, as we’ve heard in the campaign recently. It’s not simply God they’re talking about, it’s a particular kind of God, and also I think a longing for a more Christian America.

GROSS: I assume you’ve been following the Democratic and Republican primary campaigns. Are there statements you’ve heard candidates make pertaining to religion that you have found troubling in a multicultural country that includes a lot of people like you, who are secular?

JACOBY: The most troubling statement is, is that – made by Ted Cruz – which is, nobody should be president who doesn’t begin his day on his knees. I find that what he’s saying is no nonreligious person has the right to be president of the United States. I find that deeply troubling. I find it troubling that religious people don’t find it troubling. You know, a person can be religious and still respect secular values and not talk about Jesus all the time as though every American believed in Jesus. President Jimmy Carter is a very good example of that. A devout Baptist, he left the Southern Baptist convention in which he was raised because of disagreements among other things with its views about women, but he’s still a devout Baptist in his own way. But who, by the way, in the tradition of the first Baptists who joined with freethinkers to ratify a constitution that makes no mention of God, Jimmy Carter is that kind of Baptist. That kind of religious person who respects not only other religions but secular people is fine, but the kind of person who talks on the campaign trail as if to be a decent person or a decent public official, you have to have deep faith in God and practice a religion and that there’s something second-class about people who don’t, that is deeply troubling to me.

And that’s maybe one reason it’s worth trying to make atheism more visible and available to more people, so that that way of thinking will become less popular.