※ 引述《catawu ( ggg)》之銘言：
: ※ 引述《staminafish (再見了)》之銘言：
: : 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
: : 請問這個論證為何是一個無效論證呢?
: : 我唯一想到的可能是第一個前提丐題
: : 但要如何修正才會成為一個有效論證呢?
: : 請各位前輩告訴我
: : 我想了很久想不出來> <
: : 謝謝
: 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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