halacha - necessary truth or contextual truth?

Sorry for the lack of posting lately. The needs of my "real" job have been too demanding to make time for blogging lately.

I wanted to offer a response to a post over at Havolim, where Barzilai poses the following question: given opinions X and Y regarding an issue of halacha, if a posek decides that opinion X is true, then why in a case of hefsed merubah, tza'ar, or other such situations, does the posek sometimes allow opinion Y to be followed? If X is true, then shouldn't we be bound by the truth regardless of the circumstances?

The answer that Barzilai presents is that when a posek decides to accept X over Y it is not a statement about the truth-value of X or Y, but simply a procedural rule. When circumstances dictate, different procedural rules may come into play.

I would think one can make a pretty good case that more than procedural rules are at play here. The question seems to boil down to whether halachic truth is a necessary truth, e.g. truth like 2+2=4 is true. 2+2=4 is true at all times and circumstances; tza'ar or hefsed merubah will not suddenly allow 2+2 to equal 5. One cannot create a universe that obeys laws of reason that will allow 2+2 to equal 5. Can the same be said of halachic truth?

If I say "I have dark hair", that sentence is definitely true compared to everyone else in my family. In fact, it is true compared to a lot of other people. But if I moved to some desert island where everyone had pitch black tar colored hair, that true sentence would suddenly ring false. For certain statements, framework and context are necessary to establish meaning.
Instead of looking at halacha in absolute terms, perhaps statements need to be evaluated contextually.

Instead of using hefsed and tza'ar as examples, let me offer a different example. Assuming one lived in R' Eliezer's town and followed his opinion that machshirei milah are doche Shabbos, does it make sense to say that one is a mechalel Shabbos but procedurally Bais Din does not punish for that crime in these circumstances? Or does it make more sense to say that in the context of R' Eliezer's town, preparing machshirei milah on Shabbos is not considered chilul Shabbos?

To flip things l'kula and use a case Barzilai offers, if the majority of the world paskens agains the Tosfos RI"D and is not machshir "tein get al gabei sela", does someone who pasken like the Tosfos RI"D merely imfringe on a procedural rule, or has he violated a truism of hilchos ishus? I would contend the latter. If it's just a procedural rule that is violated, why does violating procedure here produce a mamzer, but violating procedure is other cases is just a lav?

I think there is one other approach one might take to address this problem. Truth values are relevant if we are discussing logocal statements, not if we are comparing values. Halacha is perhaps a value system, not a logic system. All things being equal, opinion X may reflect our values. But when in conflict with other more primary values such as the preservation of life, property, etc., perhaps opinion X must be sacrificed for the sake of preserving the greater good that the halachic system recognizes.

Good read Havolim - he has more to say than I can summarize and is always worth your time.