Tom L. Beauchamp of Georgetown is one of the founding fathers of contemporary bioethics, and is particularly influential as one of the co-authors (with James Childress) of PRINCIPLES OF BIOMEDICAL ETHICS, first published by OUP over 25 years ago and a true cornerstone of contemporary bioethics. This volume is both an introductory textbook as well as a definitive expression of what is known as the dominant "principlist" approach which views bioethical reasoning developing out of four key principles: respect for autonomy, nonmaleficence, beneficence, and justice. This view has been highly influential over the last two decades and has set the agenda for the field. This volume collects Tom Beauchamp's 15 most important published articles in bioethics, most of which were published over the last 25 years, and most of which have a strong connection to the principlist approach. Most of the essays included here augment, develop, or defend various themes, positions and arguments in that earlier book, both adding depth as well as taking off in new directions. Among the topics discussed are the historical origins of modern research ethics, to moral principles and methodological concerns. This volume includes a new introduction to explain the history of the essays and their relationship to the principlist theory.