Peter Thiel’s new book, “Zero to One: Notes on Startups, or How to Build the Future,” published last week, has enjoyed the kind of carefully calibrated rollout befitting a billionaire Silicon Valley entrepreneur, including a talk at Harvard Business School, an admiring cover story in Fortune and a party at the Four Seasons hosted by the financier Henry R. Kravis.

So on Friday night, what was Mr. Thiel, the co-founder of PayPal, doing publicly debating the future of technology with David Graeber, an anarchistic anthropologist who helped plan the Occupy Wall Street movement?

That question was certainly on the minds of some of the nearly 200 people who filled the stately library of the General Society of Mechanics and Tradesmen of the City of New York on West 44th Street in Manhattan, where the debate was held.

“I’m a big fan of David Graeber,” said Rick Carp, a magazine researcher, who was clutching a copy of “Total Liberation: The Power and Promise of Animal Rights and the Radical Earth Movement.” (A few seats away, a woman who identified herself as a junior portfolio manager at an investment firm was reading the more equation-heavy “Introduction to Statistical Learning.”)