sufficient reason

noun philosophy
  1. the principle that nothing happens by pure chance, but that an explanation must always be available
  2. the view that such an explanation is a reason for God to have chosen one alternative rather than another
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012