※ 引述《catawu ( ggg)》之铭言： : ※ 引述《staminafish (再见了)》之铭言： : : 1.If everyone promotes his/her own greatest good, then the greatest good : : for all will result. : : 2.We ought to promote the greatest good for all : : _______________________________________________________________________ : : Everyone ought to promote his/her greatest good : : 请问这个论证为何是一个无效论证呢? : : 我唯一想到的可能是第一个前提丐题 : : 但要如何修正才会成为一个有效论证呢? : : 请各位前辈告诉我 : : 我想了很久想不出来> < : : 谢谢 : The problem is partly from the concept of obligation(ought to) is not a : suitable concept for the standard formalization of first order logic. Let : OUG- be the modal operator stand for "It ought to be the case that...", : (moral necessity), we can formalize the argument as following: : If P then Q : OUG-Q : ___________________ : OUG-P : Is this a valid argument? : Sry I am tired, lets talk tomorrow.................. The agument seems invalid even in Mally's deontic logic. From my opnion what we need may be an axiom: (((If P then Q) and OUG-Q) then OUG-P). This axiom is quite like the doctrine of consequencism: If some act has the right consequence then the act is right. But it seems not comletely equvilent each other since this axiom seems more general than consquencism's claim. --

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