Gillian Sorenson argues that 'Even superpowers need friends.' To fight those crises — like terrorism, epidemics, flows of refugees -- which cross borders without passports, the U.N. must serve as the central forum for action.  Sorenson, who served from 1997 to 2003 as assistant secretary-general for external relations at the U.N., is a graduate of Smith College and studied at the Sorbonne. From the Series:UVA NewsMakers 2005