Experimenting with human subjects is going on in many fields of scientific and technological progress. It is designed to replace the overall instruction by natural, occasional, and cumulative experience with the selective information from artificial, systematic experiment which physicial science has found so effective in dealing with inanimate nature. Of the new experimentation with man, medical is surely the most legitimate; psychological, the most dubious; biological (still to come), the most dangerous. I have chosen here to deal with the first only, where the case for it is strongest and the task of adjudicating conflicting claims hardest. When I was first asked1 to comment “philosophically” on it, I had all the hesitation natural to a layman in the face of matters on which experts of the highest competence have had their say and still carry on their dialogue. As I familiarized myself with the material,2 any initial feeling of moral rectitude that might have facilitated my task quickly dissipated before the awesome complexity of the problem, and a state of great humility took its place. The awareness of the problem in all its shadings and ramifications speaks out with such authority, perception, and sophistication in the published discussions of the researchers themselves that it would be foolish of me to hope that I, an onlooker on the sidelines, could tell those battling in the arena anything they have not pondered themselves. Still, since the matter is obscure by its nature and involves very fundamental, transtechnical issues, anyone’s attempt at clarification can be of use, even without novelty. And even if the philosophical reflection should in the end achieve no more than the realization that in the dialectics of this area we must sin and fall into guilt, this insight may not be without its own gains.