From such an unlikely beginning — a self-described “religious weirdo” enrolling in an elite divinity school — has grown a fascinating phenomenon. Now in her final year at Harvard, Ms. Thurston is a central figure in a boomlet of students who are secular or unaffiliated with any religious denomination, commonly known as “nones,” attending divinity school. While Harvard may be the center, nones can be found at other divinity schools around the country, especially those inclined toward theologically and politically liberal Protestantism, like Chicago Theological Seminary.

Two factors are driving this surge. First, the proportion of nones in the United States has grown to about a third of all millennials, those born between 1981 and 1996, according to the Pew Research Center. Second, divinity school offers even atheists and spiritual seekers a language of moral discourse and training in congregational leadership. The traits appeal to nones who aspire to careers in activism, social work, chaplaincy or community organizing rather than taking to a pulpit.

“Nones are not entirely opposed to religious traditions, though they don’t attach to a specific one,” said Eboo Patel, the founder and president of Interfaith Youth Core, who has seen the trend while visiting campuses. “No small part of them are attracted to the search for social justice and for spiritual meaning. And they recognize those things as the fruits of religious tradition. So it makes sense to go to a place where you can study religious tradition.”

Within higher education, divinity programs often stand apart from the cult of relativism in the liberal arts and the utilitarian emphasis in professional schools focusing on business and law, for example.

“If you were simply looking for the skills, you might go to the Kennedy School of Government,” said the Rev. Dudley C. Rose, the associate dean for ministry studies at Harvard. “And philosophy and liberal-arts fields have given up on the project of finding a moral language, an articulation of values. That language isn’t found in many places. And when you find it, it’s not easy to abstract it. You have to connect it to a tradition.”