>Maybe Kennth has in mind something like the following. There is only one
>truth, so that versions that differ from it are just false.
This would be treating truth in a non-propositional form, it is so 18th century. Habermas is beyond this. We can no longer talk about truth in a representationalist way, the truth we have takes the form of propositional statement about the world. They only have meaning in the sense of validity.
If only one person in the world see the world in the way that they see it, they may in fact have the truth, but we institutionalize them because it they are deemed insane. I'm not saying it is good, right, correct or anything like that, but 'truth' is something that we identify as truth through the idea of validity.
We ought to have universal health care.
If we all agree, then this statement can be considered valid. Its validity, in principle, is open to criticism from any person or any direction. There is no such thing as Truth, only validity, which is always subject to revision, insofar as we do not see ourselves as gods.
>... there are other kinds of truth than the factual propositional...
And I would respond by saying that outside the propositional model, no understanding of truth can withstand the criticism that has already be leveled against it. If you want to reserve the idea of truth for something that isn't universal and is decoupled from a concept of knowledge, that's fine, but why would you want to do this other than to supply ammunition for idiots who want to say that the earth is flat, and we know this because it looks flat to me. I always try to think the most unfair situation: how could this concept be abused? The propositional model of truth, which relies on consensus, seems to me to be the least authoritarian concept of truth that we can have, and all it requires is reasoning and communication. In any event, any definition of truth one wants to adopt must be acceptable to other people, and thus only achieves legitimacy through its acceptance by others... in other words, one has to accept argumentation from the get go, ie. you can't use a propositional form (a truth claim about truth) to make a case for non-propositional understanding of truth....).
ken