George Leef of the Pope Center and Prof. James Sterba of Notre Dame have had several debates on affirmative action that are more enlightening than most. Sterba stresses the ostensible benefits (in my view, the considerably less than half of the glass that is full) and Leef surveys the costs (again in my view, the considerably more than half of the glass that is empty … but still expensive).
Take a look at an earlier debate here, and a more recent one here.
