Appeals to human nature have fallen out of favour among contemporary philosophers. A variety of charges have been raised, such as: (a) that given the rise of modern science and value pluralism, the notion of 'human nature' cannot have a substantive role to play in moral enquiry, or (b) that the invocation of human nature has been irreparably damaged by its use throughout history to justify gender and racial oppression. My aim in this book is to offer responses to such objections and to argue that the notion of human nature remains indispensable for ethics. I will contend that, once suitably reinterpreted, appeals to human nature can play a powerful role in our ethical theorizing. To carry out this task I first clarify the concept of human nature to extract a notion that can play a fruitful role in moral discourse. I then go on to examine the way that human nature has played an important role in the history of philosophy by turning to important thinkers from both the East and the West, and also by drawing upon recent developments in evolutionary and developmental psychology.The book is divided into four parts. Part I focuses on the concept of human nature by examining the most influential objections of contemporary philosophers against its use in ethics. In this section, I aim to clarify some of the current confusion surrounding the notion of human nature and to identify a target concept that can play a substantive role in normative enquiry. Part II examines how some prominent Western philosophers have deployed a conception of human nature in their ethical investigations, with a particular focus on how their conceptions of human nature influenced their accounts of virtue and moral development. I do this by examining the works of a number of philosophers of historical significance that develops an account of human nature including Plato, Aristotle, Aquinas, Hume and Nietzsche. Part III turns to philosophers in the East and examines the way that diverging conceptions of human nature deeply influenced their accounts of ethics, especially their theories of moral development. Here I focus on the writings of early Confucians including Confucius, Mencius, Xunzi, and Korean Neo-Confucians including T'oegye and Yulgok. (This narrower attention on Confucian and Neo-Confucian thinkers and the exclusion of other prominent Eastern philosophical traditions such as Buddhism and Daoism is mainly motivated by the goal of providing a deeper treatment of one significant Eastern tradition.) Part IV examines some of the recent developments in evolutionary and developmental psychology, including the recent work of the Paul Bloom and Jonathan Haidt, and analyses the implications of such empirical work on moral philosophy, especially how they might advance our understanding of human nature.