Paul Benacerraf has dominated the philosophy of mathematics in the past 25 years. Arguments derived from Benacerraf's analyses of the concept of number and the tension between the epistemology and the semantics of matematics are widespread in the rest of philosophy, particulary the philosophy of langauge and metaphysics. This volume contains ten original essays, discussing Benacerrafian themes within and outside the philosophy of mathematics, and a new essay, "What mathematical truth could not be" by Benaceraff.Within the philosophy of mathematics, the essays discuss the perennial appeal of Platonism in the philosophy of mathematics, the indeterminacy of mathematical ontology, and the legacy of the logicism of Frege and Russell. More general topics discussed include the concept of truth, indeterminacy arguments in ontology, and the status of stipulation in human knowledge. The contributors include Paul Benacerraf, George Boolos, John Earman and John Norton, Richard Grandy, Jerrold Katz, Penelope Maddy, Adam Morton, Richard Jeffrey, Robert Stalnaker, Mark Steiner and Steven Wagner.