All semester, we've been having substantive and challenging conversations in our Tuesday evening ethics seminar.  Usually, a guest talks about his or her area of expertise and then we launch into questions and answers and lively discussion.  Last week, we invited 4 MIT students to talk about their active participation in social, environmental, or political issues.  The presentations were fascinating and inspiring.  What we learned was that the presenters had chosen a specific arena in which to be active.