WASHINGTON — Two years and 144 cases have passed since Justice Thomas last spoke up at oral arguments. It is a period of unbroken silence that contrasts with the rest of the court’s unceasing inquiries. Hardly a case goes by, including two appeals that were argued yesterday, without eight justices peppering lawyers with questions. Oral arguments offer justices the chance to resolve nagging doubts about a case, probe its weaknesses, or make a point to their colleagues.

Left, right, and center, the justices ask, and they ask, and they ask. Sometimes they debate each other, leaving the lawyer at the podium helpless to jump in. “I think you’re handling these questions very well,” Chief Justice Roberts quipped to a lawyer recently in the midst of one such exchange. Leaning back in his leather chair, often looking up at the ceiling, Justice Thomas takes it all in, but he never joins in. Yesterday was no different; he said nothing. He occasionally leans to his right to share a comment or a laugh with Justice Breyer. Less often, he talks to Justice Kennedy, to his immediate left.

Justice Thomas, characteristically, declined to comment for this article. But in the course of his publicity tour for his autobiography, “My Grandfather’s Son,” the 59-year-old justice discussed his reticence on the bench on several occasions. The questions may be helpful to the others, Justice Thomas said, but not to him.

“One thing I’ve demonstrated often in 16 years is you can do this job without asking a single question,” he told an adoring crowd at the Federalist Society, a conservative legal group. The book tour showed that the topic comes up even among friendly audiences. Indeed, Justice Thomas’s comment was provoked by this question: Why do your colleagues ask so many questions? His response: “I did not plant that question. That’s a fine question. When you figure out the answer, you let me know,” he said.