Last year, a report from Harvard University set off alarm bells, because it showed that the proportion of students in the United States completing bachelor’s degrees in the humanities fell from 14 percent to 7 percent.

Even elite universities such as Harvard itself have experienced a similar decrease. Moreover, the decline seems to have become steeper in recent years. There is talk of a crisis in the humanities.

I don’t know enough about the humanities as a whole to comment on what is causing enrollments to fall. Perhaps many humanities disciplines are not seen as likely to lead to fulfilling careers, or to any careers at all. Maybe that is because some disciplines are failing to communicate to outsiders what they do and why it matters. Or, difficult as it may be to accept, maybe it is not just a matter of communication: Perhaps some humanities disciplines really have become less relevant to the exciting and fast-changing world in which we live.

I state these possibilities without reaching a judgment about any of them. What I do know something about, however, is my own discipline, namely philosophy, which, through its practical side, ethics, has made a vital contribution to the most urgent debates in which we can engage.

I am a philosopher, so you would be justified in suspecting that there is a bias in my view. Fortunately, I can draw on an independent report by the Gottlieb Duttweiler Institute (GDI), a Swiss think tank, to support my claim.

GDI recently released a ranked list of the top 100 Global Thought Leaders for 2013. The ranking includes economists, psychologists, authors, political scientists, physicists, anthropologists, information scientists, biologists, entrepreneurs, theologians, physicians and people from several other disciplines. Yet three of the top five global thinkers are philosophers: Slavoj Zizek, Daniel Dennett and me. GDI classifies a fourth, Jurgen Habermas, as a sociologist, but the report acknowledges that he, too, is arguably a philosopher.

The only Global Thought Leader in the top five not involved in philosophy is Al Gore. There are more economists in the top 100 than thinkers from any other single discipline, but the top-ranking economist, Nicholas Stern, ranks 10th overall.

Can it really be true that four of the world’s five most influential thinkers come from the humanities, and three or four of them from the field of philosophy? To answer that question, we have to ask what GDI measures when it compiles its ranking of Global Thought Leaders.

GDI aims to identify “the thinkers and ideas that resonate with the global infosphere as a whole.” The infosphere from which the data are drawn may be global, but it is also English-language only, which may explain why no Chinese thinker is represented in the top 100. There are three eligibility requirements: One has to be working primarily as a thinker; one must be known beyond one’s own discipline; and one must be influential.

The ranking is an amalgam of many different measurements, including how widely the thinkers are watched and followed on YouTube and Twitter, and how prominently they feature in blogs and in the wikisphere. The outcome indicates each thinker’s relevance across countries and subject areas, and the ranking selects those thinkers who are most talked about and who are triggering wider debate.

The rankings will no doubt vary from year to year. But we have to conclude that in 2013 a handful of philosophers were particularly influential in the world of ideas.

That would not have been news to the Athenian leaders who considered what Socrates was doing to be sufficiently disturbing to put him to death for “corrupting the youth.” Nor will it be news to anyone familiar with the many successful efforts to bring philosophy to a broader market.

There is, for example, the magazine Philosophy Now, and equivalents in other languages. There are the Philosophy Bites podcasts, many blogs, and free online courses, which are attracting tens of thousands of students.

Perhaps the growing interest in reflecting on the universe and our lives is the result of the fact that, for at least a billion people on our planet, the problems of food, shelter, and personal security have largely been solved. That leads us to ask what else we want, or should want, from life, and that is a starting point for many lines of philosophical inquiry.

Doing philosophy – thinking and arguing about it, not just passively reading it – develops our critical reasoning abilities, and so equips us for many of the challenges of a rapidly changing world. Perhaps that is why many employers are now keen to hire graduates who have done well in philosophy courses.

More surprising, and more significant still, is the way in which taking a philosophy class can change a person’s life. I know from my own experience that taking a course in philosophy can lead students to turn vegan, pursue careers that enable them to give half their income to effective charities, and even donate a kidney to a stranger. How many other disciplines can say that?

Peter Singer is a professor of bioethics at Princeton University and laureate professor at the University of Melbourne. His books include “Practical Ethics,” “One World,” and “The Life You Can Save” and the forthcoming “The Point of View of the Universe” (co-authored with Katarzyna de Lazari-Radek). THE DAILY STAR publishes this commentary in collaboration with Project Syndicate © (www.project-syndicate.org).