When science takes man as its subject, tensions arise between two values basic to Western society: freedom of scientific inquiry and protection of individual inviolability.... At the heart of this conflict lies an age-old question: When may a society, actively or by acquiescence, expose some of its members to harm in order to seek benefits for them, for others, or for society as a whole?

I argue that the increase in identification of human subjects as potentially vulnerable provides evidence for a transition in human research practice analogous to changes that have occurred in implementation of environmental policy. More specifically, the increasing identification of subjects as vulnerable corresponds to de facto acceptance of what has been called “the precautionary principle” in environmental policy.