For this particular question, Justice Thomas wasn’t donning a robe.

Tony Mauro writes at the Legal Times:

Justice Clarence Thomas Asks a Question — at Yale

Religion in the Public Service: A Conversation with Clarence Thomas and John Danforth from Yale Law School on Vimeo.

A weighty discussion at Yale Law School on the role of religion in public service suddenly turned lighthearted during a recent exchange between U.S. Supreme Court Justice Clarence Thomas and his mentor, former U.S. senator John Danforth.

The Feb. 12 discussion between Thomas and Danforth, both Yale Law School alumni, was led by their onetime professor Guido Calabresi, a senior judge on the U.S. Court of Appeals for the Second Circuit.
They delved into their own religious views, with Thomas acknowledging that he was not very religious—or kind—during his years in higher education. “I was more consumed with revolution than going to visit my grandparents,” Thomas said. “I was a tough person to be around.”

Thomas found religion again as an adult, but he said, “I don’t see it in public life as something to impose on other people.” He also spoke of the difficulty of dealing with death penalty cases as a judge, and said he still hasn’t “figured out” why the religion clauses of the First Amendment restrict states as well as the federal government.

For his part, Danforth said religion and public life should have a common mission of uniting the nation. “Holding things together is the project of our country,” Danforth said, “and it is also the meaning of religion.”

That is when Thomas interposed a question, which he said was “a little unfair,” but he asked it anyway: “What would you tell Frederick Douglass on slavery?” In context, it appeared Thomas was asking whether holding the nation together was always the highest goal, even in the face of slavery.