We present, in a synthetic way, some of the main findings from five studies that were conducted in the field of empirical bioethics, using the Functional Measurement framework. These studies were about (a) the rationing of rare treatments, (b) adolescents’ abortions, (c) end-oflife decision-making regarding damaged neonates, (d) end-of-life decision making regarding terminally-ill patients, and (e) sexuality among persons with learning disabilities. The paper also discusses what these findings tell us about the relative importance of the four principles of bioethics that are generally considered as fundamental. Two of the four principles—autonomy and justice—seem to dominate lay people’s shared beliefs about bioethics issues. The principle of autonomy is clearly central, and the principle of justice is subordinated to the autonomy principle: Each patient, irrespective of his/her characteristics, has the right to have his/her autonomy of decision respected. The two other principles – benevolence and nonmalfeasance – appear as peripheral ones. Once the autonomy principle is respected and the justice principle applies, acting in a benevolent way and not acting in a malevolent way become simple implications. When the patient has lost his/her autonomy, however, these two principles (re)gain importance.