Doctor of Philosophy可译为博士。
(Education) a doctorate
awarded for original research in any subject except law,
medicine, or theology. Abbreviation: PhD or DPhil
——Collins English Dictionary – Complete and Unabridged ? HarperCollins Publishers 1991, 1994, 1998, 2000, 2003的释义
a doctor's degree awarded for advanced studies in the humanities or the social, behavioral, or pure sciences
——Random House Kernerman Webster's College Dictionary, ? 2010 K Dictionaries
Ltd. Copyright 2005, 1997, 1991 by Random House, Inc.的释义
第一种释义的重点是：除了法学、医学或神学外的博士学位；
第二种释义的重点是：人文学科（历史、哲学、文学等）、社会学、行为科学或者理科博士。
所以，个人认为翻译为博士较好。