New Orleans — Prostitution. Polygamy. Premarital sex.

And that’s just the Old Testament.

The Bible is filled with mixed messages about human sexuality, says Jennifer Wright Knust, a professor of religion at the Boston University School of Theology, and that makes it a less-than-useful rule book for sex.

“The Bible fails to offer girls — or anyone — a consistent message regarding sexual morals and God’s priorities,” Knust wrote in the introduction to her 2011 book, “Unprotected Texts: The Bible’s Surprising Contradictions about Sex and Desire.”

On Feb. 13, Knust appeared at the Greer-Heard Point-Counterpoint Forum at the New Orleans Baptist Theological Seminary, debating sex and the Bible with more conservative theologian Ben Witherington III.

Lists of rules in some books of the Bible are contradicted by the behavior of God’s people in other books, Knust said at the forum.

The book of Deuteronomy condemns premarital sex, yet Song of Songs seems to revel in it, she said. Prostitution is sometimes objectionable, she said, but Judah in Genesis has no problem visiting a prostitute (who turns out to be his daughter-in-law tricking him).

The problem with using the Bible as a sexual guide is that many interpreters pick out a few verses or stories and assume that those passages “stand in for the entire biblical witness,” Knust said.

“The Bible, however, is a diverse collection of books written over the course of about 1,000 years by human actors living in circumstances that changed dramatically ...,” she said. “As such, the Bible cannot be expected to offer a single or consistent message on anything, including sex, even if some of us do regard this collection as divinely inspired, as I do.”

Sex has always been a difficult subject for churches.

“I think we may have gotten the same mixed messages about sex growing up,” Witherington said. “The message I got from my junior high (youth) leader when he had his little talk about the birds and the bees was this: Sex was dirty. Save it for the one you really love.”

This outlook doesn’t align with the Bible, which shows a “robust belief in the goodness of human sexuality and sexual sharing in the right context,” Witherington said.

From Knust’s point of view, the Bible has been misused for centuries as readers pick and choose which passages to ignore and which to use to condemn others, she said.

“As a historian, I know this is a very old game, this habit of employing select passages of sacred Scripture as a carving knife to slice human communities (into) those who are deserving and those who are not,” Knust said during the forum. “Apparently the Bible allows those who are wearing the right spiritual and doctrinal glasses to glimpse God’s own judgments and therefore to discern who is to be regulated to Gehenna and not only by God.”

Knust’s book cites scholarship that questions whether David and his friend Jonathan, the son of King Saul, had a sexual relationship, at which 2 Samuel may hint.

And the story of Sodom and Gomorrah may have had several meanings to early readers — the importance of hospitality or a warning against attempts to have sex with angels — and not just the anti-homosexual story modern readers take, she said.

Witherington took umbrage with her interpretations.

Stories about God’s people doing wrong should not be confused with the clear commands of the Scriptures, said Witherington, a professor at Asbury Theological Seminary.

The Bible, he said, is clear about sexual expectations.

“The Bible is replete with examples of patriarchs, or prophets or priests or kings or even apostles behaving badly,” Witherington said during the forum in New Orleans. “The fact that the narrative is honest, (that it) presents people to us warts, wrinkles and all, is one of the great things about the Bible. But at the same time we have such stories of misbehavior, we also have clear statements condemning prostitution and bad behavior.”

To create a set of sexual ethics, Witherington said, Christians must focus on the New Testament, not the old covenant between God and his people. The laws of the Old Testament were there to “limit sin, not license it,” he said.

For example, Witherington said, Jesus told his listeners that they were previously allowed to divorce because their hearts “were hard.”

They were also told they could take revenge, as long as it was only “an eye for an eye,” Witherington said, but under the new covenant, believers would be held to a higher standard.

“To whom more is given, more is required,” Witherington said.

The New Testament writers were very clear, Witherington said, about sex.

“The way marriage is viewed in the New Testament is as heterosexual monogamy,” he said. “That is how one flesh is possible. That is how the commandment to be fruitful and multiply can be carried out.”

Boundaries to sexual intimacy are clear, he said.

“Sexual intimacy outside of what the Bible calls love is not merely inappropriate,” he said. “It is immoral. You are not supposed to totally give yourself physically to someone you do not totally trust and totally love. Physical intimacy is not a goal in itself. It is a means to express deep love, deep commitment, deep relationship and above all else it is a means of procreation.”

For Knust, the final authority in all matters is Christ, she said. Christians worship him, “the incarnate word of God, not the words of the Bible,” she said.

So, she said, in all matters, including questions of sexual right and wrong, Christians should lean in favor of the principle “love your neighbor as yourself.”

Appealing to the principle of love could change the debate, she said, “from the alleged content of what the Bible says to what the loving thing to do might actually be.”