Tom Beauchamp and James Childress have always maintained that their four principles approach (otherwise known as principlism) is a globally applicable framework for biomedical ethics. This claim is grounded in their belief that the principles of respect for autonomy, non-maleficence, beneficence and justice form part of a ‘common morality’, or collection of very general norms to which everyone who is committed to morality subscribes. The difficulty, however, has always been how to demonstrate, at least in the absence of a full-blooded analysis of the concept of morality, whether the four principles are foundational, and so globally applicable, in this way. In the recently published sixth edition of Principles of Biomedical Ethics, an imaginative and non-question-begging empirical method of determining the common morality's norms is suggested. In this paper, I outline this method, before arguing that it is difficult to see how it might be thought to achieve its purpose.