Justice Breyer said last week that in a shrinking and increasingly interconnected world, understanding what is going on abroad is necessary and helpful, whether the topic is national security, free speech, securities regulation or antitrust law. As for citing the decisions of foreign and international tribunals, he said, that issue was a distraction. The decisions were not binding on American courts, he said, but they could be instructive.

“The argument politically is what I call the froth on the surface,” he said. “It has very little to do with what’s going on.”

“What I’m trying to show is that the whole argument is beside the point,” he added. “The world we’re operating in is one in which by and large everyone believes you have to know something about what’s going on abroad.”

He said he understood why some people disagreed with him. “I think their real motive is to preserve our system, our constitutional values: democracy, human rights, rule of law,” he said. “That’s the correct motive.” He did allow, though, that “it’s crossed my mind that people who don’t like the results in these very highly visible and controversial cases decide to blame the foreign law.”

Justice Breyer spends a fair bit of time abroad. In 2013 and 2014, according to financial disclosure forms, he visited Britain, Canada, France, Luxembourg, Monaco, Norway and Sweden. He was inducted in 2013 as a foreign member of France’s Académie des Sciences Morales et Politiques, one of the five academies of the Institut de France.

He said he found it useful to compare notes with foreign judges. In the book, he noted that some Americans were wary of such interactions, partly because they saw “judges throughout the world as belonging to the same social caste — one sharing generally ‘leftish’ political views.” But he said judges facing similar problems could learn from each other.

On his own court, Justice Breyer was in the majority 92 percent of the time in the last term, four percentage points ahead of the usual leader, Justice Kennedy. That was satisfying, he said. “When you reach a conclusion, and you put words down on the paper, and you’ve written an opinion, of course you’re pleased if others agree,” he said. “I mean, if you didn’t think it was right, why would you write it?”