P1: Every possible meaning of x is subject to change unless there is a being to which an unchanging definition of x corresponds.
P2: If every possible meaning of x is subject to change, x lacks meaning that is not subject to change.
P3: If x lacks meaning that is not subject to change, x has no objective meaning.
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Let “GPWB” be Sam Harris’ concept of objective moral truth (Greatest Possible Well Being).
P1a: Every possible meaning of GPWB is subject to change unless there is a being to which an unchanging definition of GPWB corresponds.
P1b: Harris denies the existence of a perfectly good/well being to which GPWB corresponds.
P1c: [P1a, P1b.] Every possible meaning of GPWB is subject to change.
P2a: If every possible meaning of GPWB is subject to change, GPWB lacks meaning that is not subject to change.
P2b: [P1c, P2a.] GPWB lacks meaning that is not subject to change.
P3: If GPWB lacks meaning that is not subject to change, GPWB has no objective meaning.
C: [P2b, P3.] GPWB has no objective meaning.
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This post also appeared on Examiner.com.
Ichthus77 
I think that there may be a kind of circularity in the argument. You initially define objective meaning in terms of exemplification. But by definition Harris' argument cannot meat this definition.
Not sure if this is a fair objection, but I think that the fact that you define objective meaning in terms of exemplification begs the question against Harris in this case. The argument should be to establish P1/P2 because from those it follows Harris' project fails.
J.W., I don't think I am totally understanding you. If you forget about Harris' argument and plug something else into 'x' do you get the same feeling of circularity? How can exemplification (correspondence) not be a requirement for objective meaning? I'm still learning here, so perhaps you can point me to some alternative theories of objective meaning which do not involve correspondence. Harris goes as far as saying he is talking 'about' conscious beings (he appreciates 'correspondence') but he does not think it through far enough. Thanks for helping me think this through.
I've modified it, let me know if it made a difference.
JW, I think I see what you mean now. It has to do w/ how Sam Harris uses the word “objective”. I just edited the article to include a link to a comment by Jime to another of my Sam Harris articles which discusses this.
As you are well aware, in his recent debate with William Lane Craig, Sam Harris says “We can speak objectively about a certain class of subjective facts that go by the name of morality,” and Craig appropriately asks “Is the wrongness of an action a subjective fact?”
This current article makes it clear that Sam is equivocating on the word objective in “objective moral truth”.