Tony Blair has taken on several new roles since quitting as prime minister
Tony Blair has taught his first seminar of the "faith and globalisation" course he will lead at Yale University.
During the seminar, he said that religious faith inspired some people to do harm but it also had the potential to do great things in the modern world.
The course will explore the public roles of religious faiths in the context of globalisation.
In May Mr Blair launched a faith foundation to tackle poverty, challenge conflict and unite world religions.
During the seminar, Mr Blair said: I genuinely believe that the issue to do with faith and
globalisation is the single-most determining issue of the 21st century.
"Faith is important because it motivates people...to do harm. But it also has the potential to do good."
In an interview with the university's Yale Daily News, Mr Blair admitted to being nervous about the job.
"I was never a star student, and I'm coming along mixing with a whole lot of people who I'm sure are a whole lot more clever and smarter than I am," he said.
According to the university, hundreds of students applied for places on the course.
However, Yale University president Richard Levin said Mr Blair's arrival on campus had also met with controversy.
He told BBC News: "As is the case in Britain, a lot of young people are opposed to the Iraq war and so I think there are some students that would consider that a serious problem.
"But I also think our students are very excited about having the former prime minister of the United Kingdom here as a figure on campus," he added.
Mr Blair said he was partly drawn to Yale after his son Euan graduated from there earlier this year with a master's degree in international relations.
Mr Blair has also taken up lucrative jobs as an advisor to an international bank and an insurance company.
His other commitments include being the United Nations special envoy on Middle East peace and a campaigner on climate change and African poverty.