Many years ago, I read a popular book on astronomy for young people in which the author suggested that the first person to be launched into orbit around the moon would be a volunteer with no prospect of returning to earth. His place in history would be assured and he would have sacrificed his life for information of inestimable scientific value. I can’t remember if payment was suggested, but I recall my childish reaction to the proposal—surely this couldn’t be done. There are certain things that research participants should not be asked to do, no matter how important.

Undoubtedly some questions are important and seemingly of pressing urgency: the limits of human endurance to new chemical agents or biological weapons in wartime, for example. But such high risk investigations are not justifiable. Treating humans merely as a means to further knowledge dehumanises the experimental subject, no matter how informed the consent. Where risk is high, people should not …