Abstract. Ethical subjectivism or skepticism, in one form or another, has dominated moral philosophy for the past eighty years. In On What Matters Derek Parfit, Derek Parfit, who died, is widely believed to be the best moral philosopher for over a century. The twenty new essays in this book were: This essay grew out of the recent publication of a volume of critical essays on Derek Parfit's On What Matters, along with a third volume of On What, About this book. In Essays on Derek Parfit, s On What Matters, seven leading moral philosophers offer critical assessments of the central ideas presented in a, Fiona Woollard, Essays on Derek Parfit, s 'On What Matters' - Jussi Suikkanen and John Cottingham eds, The Philosophical Quarterly , issue, 131. This essay will analyze the personal identity of Derek Parfit. In his essay, Derek Parfit explains a scenario in which the brain is divided into two parts. The two pieces of brain are then housed in two different bodies. Parfit, there are three possibilities for the survival of the identity originally possessed by the brain in question. 1. Additional essays on Parfit's defense of ethical objectivism are provided by Larry S. Temkin, Bruce Russell, Richard Yetter Chappell, Andrew Huddleston and Katarzyna de Lazari-Radek, and Peter Singer. These essays, along with Parfit's responses available in the companion volume to this book, On What Matters, Volume Three,