These would be roles that we do not adopt voluntarily. The roles of breather and drinker would be examples of these. They are inescapable and involuntarily in the same way that the role of believer is. Consider, for example, the role of breather. We all have to breathe and are thus in the role of breather, even if we did not voluntarily choose to be. Feldman would presumably suggest that there is a proper way to breathe well. We ought to breathe evenly, in through the nose, and out through the mouth, for example.
But consider this situation: a baby is born with a condition that does not allow him to breathe properly on his own. Presumably, it would be absurd for us to say that this baby still ought to breathe well. Feldman would likely agree that this baby is exempt from his obligation as breather. The baby cannot breathe on his own, and so is relieved of his obligation. But this assumed agreement would go directly in the face of Feldman’s argument: that ought does not imply can. The baby’s obligation to breathe well would disappear precisely because of the principle of ought implies