To what extent should we use technology to try to make better human beings? Because of the remarkable advances in biomedical science, we must now find an answer to this question. Human enhancement aims to increase human capacities above normal levels. Many forms of human enhancement are already in use. Many students and academics take cognition enhancing drugs to get a competitive edge. Some top athletes boost their performance with legal and illegal substances. Many an office worker begins each day with a dose of caffeine. This is only the beginning. As science and technology advance further, it will become increasingly possible to enhance basic human capacities to increase or modulate cognition, mood, personality, and physical performance, and to control the biological processes underlying normal aging. Some have suggested that such advances would take us beyond the bounds of human nature. These trends, and these dramatic prospects, raise profound ethical questions. They have generated intense public debate and have become a central topic of discussion within practical ethics. Should we side with bioconservatives, and forgo the use of any biomedical interventions aimed at enhancing human capacities? Should we side with transhumanists and embrace the new opportunities? Or should we perhaps plot some middle course? presents the latest moves in this crucial debate: original contributions from many of the world's leading ethicists and moral thinkers, representing a wide range of perspectives, advocates and sceptics, enthusiasts and moderates. These are the arguments that will determine how humanity develops in the near future.