At the risk of incurring everyone’s ire, let me propose something:
You guys are talking past each other.
Let’s make a distinction between two senses of the word “word”. First, we have the syllables spoken when the word is spoken: call this the “word matter”. Second, we have the word as a fixed symbol that designates one and only one particular thing: call this the “word form”. (Philosophers call this second sense of “word” a “rigid designator”). See
plato.stanford.edu/entries/rigid-designators/
There is a proposal on the table to include committed partnerships between people of the same sex as “marriages”.
Now clearly the syllables “marr-iage” can be used to indicate partnerships between people of the same sex, just as “gobbledeegook” can be used to indicate rose bushes. There is no problem with using the word matter to mean whatever we want. So, on the surface, posters like PRMerger would seem to be just wrong to say that we could not – as a culture – change the meaning of the word “marriage”.
However, suppose we take “marriage” as a rigid designator of a particular thing. The word form “marriage” is not the type of thing that can change. A language might lack a word matter to indicate this word form (an alien race might not have a word for marriage), but the word form cannot change. And this word form has a history. It simply is not plausible that, when people throughout the ages have talked about “marriage”, they *meant *something that could be entered into by two women. On this view, PRMerger and Stephen168 are exactly right.
But the syllables don’t matter. If the language changes to use the syllabes “marr-iage” to indiscriminately refer to gay or straight partnerships, that will not change what marriage is.
Supporters of gay marriage are not trying to do something impossible. (If they were, it would be silly to oppose it). They are trying to use language to affect reality in various ways, to appropriate evocative syllables.
In the end, there is a genuine disagreement being discussed here. But it’s NOT a disagreement about words, so I don’t think we really need to be talking this much about words.