Now, one might try to interrupt the preceding line of thought by arguing that the additionalelement required here is not the notion of rights, but rather that of a moral duty or obligation,one which may or may not have a corresponding moral right.
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But it is doubtful that theintroduction of the notion of duty suffices to pick out justice as a specific value, in theabsence of a requirement that the duties in play have corresponding rights. After all, thequestion of which charity to support is also one of allocation, and plausibly both a matter of obligation and subject to the like cases maxim. Yet to regard all principles addressed to such aquestion as principles of justice risks effacing the distinction between justice and charity.