I suppose there are three or four reasons. The simplest reason sounds a little hokey, but it's simply because I was asked.
I've spent my life as a tenured university professor, one of the most delightful positions possible in our society, and have been asked frequently to chair different public interest things. I've almost always said yes to that over 40 years or so, subject to, “I don't think I have the qualifications,” and sometimes that's been a debate. From time to time I don't have the time. Typically it's simply because I'm doing another one. I do believe that it's a citizen responsibility, especially when you're lucky enough to be a professor of law in one of Canada's fine universities.
Second, I think it's vitally important that we have timely, predictable, first-class debates where people can make decisions on what kind of leader they want to be leading our country and what kinds of policies that person and his party should be pursuing, and be broadly engaged in the spectrum of choices that good societies have to make about where they want to take their country.
I must say, I have been somewhat worried about erosion of trust in public institutions, which moved me to write a book called Trust. It came out about six months or so ago. I think that was another compelling reason to say, “I suppose I need this like another hole in my head, but it's something I should do.”