Social movements thrive on symbolic victories, and earlier this month the campaign against fossil fuels scored a humdinger. Stanford University, responding to pressure from student environmental activists, announced that its $18.7 billion endowment would sell its stock in coal-mining companies.

Anti-coal campaigners were gleeful. “Stanford, on the edge of Silicon Valley, is at the forefront of the 21st century economy; it’s very fitting, then, that they've chosen to cut their ties to the 18th century technology of digging up black rocks and burning them,” Bill McKibben, the outspoken founder of 350.org, a group pushing for fossil-fuel divestment, wrote on his group’s website. Stanford’s decision is “a huge, huge victory,” showing that “the coal industry and other fossil-fuel industries are quickly becoming relics of the past,” Maura Cowley, who heads Energy Action Coalition, a coalition of climate-activist groups, told The New York Times.

The decision by Stanford—where I work, though I had nothing to do with the divestment move—is indeed a noteworthy shot in the culture wars over climate change. But it’s at least as noteworthy for what it doesn’t do as for what it does. In a discussion with me this week, Stanford President John Hennessy explained why university officials were careful to structure it narrowly. Students initially had asked Stanford to divest shares it holds in any of 200 publicly traded fossil-fuel companies. But, Hennessy said, the university decided that doing so would hit the school’s coffers too hard and be “hypocritical,” since Stanford, like the world, runs mostly on fossil fuel. So Stanford divested only from companies that mine coal. That step was small enough, the university decided, that it wouldn’t hurt Stanford’s investment returns—and wouldn’t invite allegations of intellectual dishonesty, given that Stanford’s home state of California, unlike many other states, gets very little of its electricity from coal.

Why do the nuances of one elite university’s coal-divestment decision matter to the country? Because Stanford is a canary in the coal mine. It’s a massive, wealthy research institution putting a lot of thought and money into trying to shift society toward a cleaner energy system. If Stanford, with all its environmental aspirations, won't cross certain lines, the rest of American society is likely to be even more hesitant to do so.

Stanford policy says that, when the university believes “corporate policies or practices create substantial social injury,” it can factor that concern into its investment decisions. The school has a history of targeted divestment from stocks it finds objectionable on moral or social grounds. In response to concern about South African apartheid, Stanford divested not from all companies selling goods or services in the country—a category that would have included a good chunk of multinational firms—but from companies that were supplying the South African apartheid regime. “It was scoped to focus specifically on companies that were enabling the government to participate in apartheid,” Hennessy said. “You try to fine-tune things.”