Bioethics is a discourse about tolerance. The recognition of humanity’s moral plurality and the idea that different beliefs and values govern issues such as abortion, euthanasia, and cloning made it imperative to structure an academic discipline that reflects on these conflicts, which are so frequent in the medical field. There are few texts on bioethics published in Portuguese, and an even smaller number authored by Brazilians. The available publications are, in general, compilations and thematic collections. This book changes the traditional style of presenting bioethics in Brazil and starts with theories and their criticisms, which allows the reader to become more familiar with the subject and reflect on situations of moral conflict.