Preface by Thomas H. Murray, President Emeritus of the Hastings Center and Chair of the Ethical Issues Review Panel for the World Anti-Doping Agency. Introduction: Human nature as a promising concept to make sense of the spirit of sport -- Part I Conceptual and Theoretical Framework -- Jan Tolleneer and Paul Schotsmans, Self, other, play, display and humanity. Development of a five-level model for the analysis of ethical arguments in the athletic enhancement debate -- Christian Lenk, Is human enhancement unnatural and would this be an ethical problem? -- Pieter Bonte, Dignified doping: truly unthinkable? An existentialist critique of 'talentocracy' in sports. - Part II Transgressing the limits of human nature -- Eric Juengst, Subhuman, superhuman, and inhuman. Human nature and the enhanced athlete -- Trijsje Franssen, Prometheus on dope. A natural aim for improvement or a hubristic drive to mastery? -- Darian Meacham, Outliers, freaks, and cheats. Constituting normality in the age of enhancement -- Part III The normative value of human nature -- Andreas De Block, Doping use as an artistic crime. On natural performances and authentic art -- Andrew Holowchak, Something from nothing or nothing from something?. Performance-enhancing drugs, risk, and the natures of contest and of humans -- Mike McNamee, Transhuman athletes and pathological perfectionism. Recognising limits in sports and human nature -- Part IV Socio-cultural and empirical approaches -- Marianne Raakilde Jespersen, "Definitely not for women". An online community's reflections on women's use of performance enhancing drugs in recreational sports -- Denis Hauw, Toward a situated and dynamic understanding of doping behaviors -- Tara Magdalinski, Restoring or enhancing athletic bodies. Oscar Pistorius and the threat to pure performance -- Part V Practices and policies -- John Hoberman, Sports physicians, human nature, and the limits of medical enhancement -- Bengt Kayser and Barbara Broers, Anti-doping policies: choosing between imperfections -- Roger Brownsword, A simple regulatory principle for performance-enhancing technologies. Too good to be true?