 abstract objects |  essential vs. accidental properties |  existence |  fictionalism: modal |  God: and other necessary beings |  haecceitism |  haecceity: medieval theories of |  identity: of indiscernibles |  identity: over time |  identity: transworld |  impossible worlds |  Lewis, David |  Lewis, David: metaphysics |  logic: free |  logic: intensional |  logic: modal |  Meinong, Alexius |  mereology |  modality: medieval theories of |  modality: varieties of |  names |  nonexistent objects |  object |  ordinary objects |  possibilism-actualism debate |  possible worlds |  rigid designators |  semantics: two-dimensional |  sortals |  substance |  temporal parts 