The U.S. Supreme Court justices. bottom row, from left: Clarence Thomas, Antonin Scalia, Chief Justice John G. Roberts Jr., Anthony Kennedy, Ruth Bader Ginsburg. Top row, from left: Sonia Sotomayor, Stephen Breyer, Samuel Alito Jr. and Elena Kagan. (Pablo Martinez Monsivais/Associated Press)

Mark Tushnet is a professor of constitutional law at Harvard Law School and the author of “In the Balance: Law and Politics on the Roberts Court.”

The Supreme Court opened its term this past week with cases about campaign finance, abortion protests, public prayer and presidential power on its docket. John G. Roberts Jr. has been chief justice since 2005, and we’ve seen enough from the Roberts court to get a sense of what we do and don’t understand about it, and to separate reality from fiction.

1. The Roberts court just calls balls and strikes.

Roberts famously said at his confirmation hearing that his job on the Supreme Court would be like an umpire calling balls and strikes , suggesting that the position doesn’t allow a justice to let his political leanings affect his decisions. The metaphor isn’t all wrong; sometimes the justices do call balls and strikes.

But as the joke goes, there are three kinds of umpires: One says, “I call ’em like they are.” Another: “I call ’em as I see ’em.” And the third, “They ain’t nothin’ until I call ’em.” The third umpire has it right, at least for the court’s most complicated cases. There’s a reason we call people like Roberts “judges” — we expect them to exercise judgment in interpreting the Constitution. Even the chief justice has said he may have pushed the image of mechanical judging too far with the umpire metaphor. In the most recent term, Anthony Kennedy joined the court’s liberals to strike down a key provision in the federal Defense of Marriage Act and joined the court’s conservatives to strike down a key section of the Voting Rights Act . It’s implausible to believe that every justice just happened to vote in a way consistent with his or her general attitudes. Those results remind us that sometimes the justices’ political views do affect how they interpret the Constitution.

2. The justices are partisans, just like Republicans and Democrats in Congress.

Justices bring general liberal or conservative attitudes to the task of constitutional and statutory interpretation. But notable exceptions such as Bush v. Gore notwithstanding, the justices usually aren’t shills for whoever happens to be leading the Republican and Democratic parties. For one thing, the justices know they’re going to be on the Supreme Court long after President Obama and House Speaker John Boehner have left office. Their visions of liberalism and conservatism have to run deeper than the passions of today’s politics.

At confirmation hearings, nominees and senators talk about judicial philosophies (if they’re Republicans) and judicial ideologies (if they’re Democrats). Those viewpoints are shaped by the justices’ backgrounds and experiences. It’s no surprise that Roberts and Samuel Alito, who worked as high-placed lawyers in Republican administrations, have conservative visions about the role of government and the Supreme Court, nor that Elena Kagan, who worked in the Clinton and Obama administrations, has a liberal one. But Roberts and Alito aren’t out to enact into constitutional law what today’s Republicans think is good policy, nor does Kagan do the same for the Democrats. After all, Roberts voted to uphold the Affordable Care Act’s “individual mandate,” and Kagan voted to strike down that law’s requirement that all states expand their Medicaid programs to cover more poor people.

3. Roberts’s vote in the Affordable Care Act case was an act of cowardice (or of statesmanship).

The chief justice agreed with his conservative colleagues that Congress didn’t have the power to require people to buy health insurance. Reports from inside the court make it clear that those colleagues were surprised, even outraged, then, when Roberts sent around a draft opinion holding that the power to impose taxes allowed Congress to penalize people for not purchasing health insurance. Conservatives outside the court said Roberts had capitulated to warnings from Obama and other liberals that the court’s credibility would suffer if it struck down the Affordable Care Act. Liberals said his vote was an act of statesmanship, taken to preserve the court’s long-term position in our system of government.

Neither view is correct. All Obama could have done to hurt the court was criticize it. And it was completely unclear in March and April 2012, when the chief justice was writing his opinion, what result would have been better for the court and for the GOP. Strike the act down, and maybe the court would save the country from a statute with disastrous consequences; uphold it, and maybe history would view the court as allowing a major advance in social welfare to go forward. Strike it down and possibly energize Democrats to turn out in November in outrage; uphold it and maybe energize Republicans to elect a president who would repeal the act. In this case, at least, Roberts simply called one ball (no power under the commerce clause) and one strike (the tax power is enough), as he saw them.

4. The Roberts court is a strong defender of free speech.

The statistics don’t bear this out. Looking at the cases in which the court has considered First Amendment claims, scholars have found that the Roberts court has given less support to the First Amendment than did the Rehnquist and Burger courts, which were not known as avid defenders of free speech.

Many of the Roberts court’s decisions finding that statutes violate the First Amendment involve campaign finance, with Citizens United only the most prominent. Others, such as a ruling invalidating a Vermont law limiting data-mining by pharmaceutical companies, have struck down restrictions on advertising and related forms of speech by corporations. These decisions should be understood in light of the court’s pro-business bent rather as simply defenses of free speech. For example, Holder v. Humanitarian Law Project upheld a federal statute making it a crime to provide “material support” to a foreign terrorist group by giving it advice on how to achieve its goals peacefully. In that decision, the Roberts court adopted a doctrine that could threaten constitutional limits on the government’s ability to punish political speech. Overall, a record worth no more than 11 / 2 cheers for free speech, not three.

5. Justice Clarence Thomas doesn’t contribute much to the court’s jurisprudence.

Thomas almost never says anything in oral arguments, because, he’s said, he thinks his colleagues talk too much. Behind the curtains, though, Thomas isn’t silent. He’s said he likes to write opinions in cases involving complicated and technical statutes, such as this summer’s decision sharply limiting scientists’ ability to get patents on human gene sequences.

On hot-button constitutional issues, he’s staked out positions about gun rights and children’s rights that are more consistently originalist than those of any of his colleagues. And his opinions on affirmative action, which quote Frederick Douglass and emphasize the importance of historically black colleges, have overtones of black nationalism. All in all, Thomas’s voice — in his opinions — is one to take seriously.

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