In academic life, false ideas are merely false and useless ones can be fun to play with. In political life, false ideas can ruin the lives of millions and useless ones can waste precious resources. An intellectual's responsibility for his ideas is to follow their consequences wherever they may lead. A politician's responsibility is to master those consequences and prevent them from doing harm. Michael Ignatieff, a former professor at Harvard and contributing writer for the magazine, is a member of Canada's Parliament and deputy leader of the Liberal Party.