Simon Blackburn, Professor of Philosophy at Cambridge University and a leading figure in ethics and philosophy of language, among other areas, will return to the Department of Philosophy at the University of North Carolina at Chapel Hill each fall, beginning in 2008 and continuing each fall for at least five of the next six years.   Blackburn, who is 63 this year, will be coming up against the mandatory retirement age in the U.K. soon.  That’s a significant coup for UNC, which already boasts one of the top ethics faculties in the U.S.