 To avoid these biases, we might stretch the veil of ignorance to obscure the generation to which one belongs—past, present or future (Brock 1994). Under a veil of ignorance so stretched, individuals might choose to participate in clinical research as long as the benefits of the practice exceed its overall burdens. One could then argue that justice as fairness gives all individuals an obligation to participate in clinical research when their turn comes. This approach seems to have the advantage of explaining why we can expose even children to some risks for the benefit of others, and why parents can give permission for their children to participate in such research. This argument also seems to imply not simply that clinical research is acceptable, but that, in a range of cases, individuals have an obligation to participate in it. It implies that adults whose turn has come are obligated to participate in clinical research, although for practical reasons we might refrain from forcing them to do so.