To resort to hypoxic air machines—would that be to cheat? This clearly depends on whether such machines are prohibited or not. So the important question is this: Should sport authorities prohibit them or not?

One way of approaching this question may be to argue casuistically. Erythropoietin (EPO) is prohibited. Blood doping is prohibited. Training at high altitude is allowed. Does the hypoxic air machine bear more resemblance to training at high altitude than to the use of EPO? If that is the case it should not be prohibited. If, on the other hand, it bears more resemblance to the use of EPO, then it should be prohibited.

However, to argue casuistically is not entirely satisfactory. Even if, through such reasoning, we reach an answer, we do not obtain a principled explanation of the answer. We may get a hint at what to do (allow or prohibit), but not at why we should do so.¹ So the question need to be posed at a more principled level: If rules against doping in sport are to be …