The Supreme Court justices asked a lot of eyebrow-raising questions Tuesday during oral arguments over same-sex marriage, including topics such as polygamy and whether opponents simply dislike gay people. Here is a sampling of the more provocative issues they raised in the hearing.

1. Are biological children the whole point of marriage?

For the states defending their right to ban same-sex unions, the central question in this case has been: What is the state’s interest in marriage? They argue that the only reason the state has a role in marriage is that it has an interest in creating incentives for parents to stay together and raise their biological children.

But that line of logic raises some uncomfortable questions, which came up in Tuesday’s arguments. Among them: Does that mean a 55-year-old woman should not be allowed to marry because she can no longer bear children? Are adoptive families somehow inferior? What of the couples who can’t or don’t want to have children? And don’t these incentives often fail, leaving moms and dads to walk away from their spouses and children?

The nation's highest court is hearing Obergefell v. Hodges, a case that examines if same-sex couples have a constitutional right to marry. Here's what you need to know about the case that could make gay marriage legal across the nation. (Julie Percha/The Washington Post)

Pressed on these hypotheticals, John Bursch, the former Michigan solicitor general who represented states that want to keep restrictive laws, offered some responses. Adoptive families are “heroic,” he said, playing a critical role when those biological families fail or fall apart. There are privacy reasons why a state cannot ask a couple about their plans to have children before giving them a marriage license, he said.

In the end, Bursch’s job was not to delve into these different scenarios but “simply to show that the state’s reason for this institution is a reason that has nothing to do, that is inapplicable, to same-sex couples,” Justice Antonin Scalia said.

But Justice Elena Kagan disagreed. “I think before something as fundamental to a society and to individuals as marriage, before an exclusion of this kind can be made in that institution, the state needs some reason for that exclusion,” she said.

2. Why didn’t the ancient Greeks have same-sex marriage?

Justice Samuel A. Alito Jr. threw Mary L. Bonauto, the attorney representing gay couples challenging states’ bans, for a loop early in the proceedings when he asked her about the ancient Greeks’ approach to homosexual relationships, even quizzing her on Plato’s views of such relationships.

The point he was trying to make was that there must have been some rational reason besides prejudice that societies have for thousands of years defined marriage as exclusively between a man and a woman. The ancient Greeks were permissive, to some degree, of homosexual relationships, and yet they did not condone same-sex marriage, Alito said.

Bonauto, apparently impatient with the line of questioning, responded, “I can’t speak to was happening with the ancient philosophers.” What matters are the principles of liberty and equality that were integral to the founding of the United States, she said.

But even Justice Stephen G. Breyer, one of the court’s reliably liberal members, thought it worth asking why it was up to the nine justices of the Supreme Court to change the long-standing institution of marriage that predates the United States to include same-sex couples.

3. Polygamy, miscegenation, incest and child brides

Proponents of a national right to same-sex marriage have argued over and over that the answer to the question of who decides about marriage is simple: People decide whom they want to marry, not the government or anyone else.

But the justices tested this contention by bringing up consensual forms of marriage that are limited or banned, such as plural marriage, marriage between blood relatives and marriage that involves minors. Some of the conservative justices asked: Would rules governing these factors also come into question if states are forced to allow same-sex couples to marry?

It’s true, marriage laws vary significantly on the other matters. While every state bars marriage between more than two individuals, it is accepted practice in some countries. New Hampshire allows girls as young as 13 and boys as young as 14 to marry with parental consent, while others peg the age at closer to 15 or 16. Some states recognize first-cousin marriages from out of state while others do not.

The liberal justices were more inclined to bring up anti-miscegenation laws, which barred or limited interracial marriages. These laws were invalidated after the famous 1967 Loving v. Virginia ruling, which has been cited as precedent by same-sex marriage supporters.

4. Would it ultimately be better for same-sex marriage if the court ruled against it?

Chief Justice John G. Roberts Jr. brought up a point that has been was raised in the past by some supporters of same-sex marriage. Wouldn’t it be better for same-sex marriage, considering how quickly views of it are changing, to let it become the norm slowly, state by state, rather than forcing it upon everyone at once the way a sweeping Supreme Court ruling would?

Some justices also asked whether it would not be better for everyone if the “social experiment” of same-sex marriage played out in some states, giving other states a window into whether it is harmful.

But Bonauto countered that “the effect of waiting is not neutral. It does consign same­-sex couples to this outlier status, and there will be profound consequences that follow from that.”

5. Isn’t this really all about hatred of gays?

Supporters of national same-sex marriage contend that laws banning same-sex marriage make sense only if you have a problem with homosexuality and homosexuals. Even if the purpose of the laws isn’t to demean gays, “it has that effect,” Bonauto said in response to a challenging question from Alito over whether she truly believes the states are motivated by prejudice.

“They encompass moral judgments and stereotypes about gay people,” she said.

But the other side tried to emphasize that this was not about animus toward gay people. They said it was about the ability of a state to establish laws that further its interest in tying children to their biological parents. And they argued that it was about the right of voters to decide on an important cultural issue.

The states don’t “intend to take away dignity from anyone,” Bursch said. “We respect all parents, and we hope that they love their children. But this court taking this important issue away from the people will have dramatic impacts on the democratic process.”

Bursch also suggested that establishing a national right to same-sex marriage could lead to more people being labeled bigots for their views. “When you enact social change of this magnitude through the federal courts, it’s cutting off that dialogue, and it’s saying one group gets their definition and the other is maligned as being irrational or filled with animus,” he said.