Hare, Singer and Gewirth on universalizability

This paper compares the attempts of hare, Singer and gewirth to provide the trivially true universalizability principle with normative content. The programs of hare and singer share an inability to convict the sincere fanatic ( the servant of an immoral but aesthetically compelling ideal) of moral inconsistency. Gewirth avoids the "fanatic" pitfall by adding some purely logical footwork; but his system too admits of important indeterminacies which may or may not prove fatal, E.G., The handling of morally tolerable coercion and of the occasional duty to repair damage caused by someone else