As I said in the OP, postmodernism IS an idea in art - we're agreed on this much. But the OP was SPECIFICALLY concerning that additional aspect of postmodernism that addresses philosophy.
I understand that is the claim you are making concerning 'additional aspects' of postmodernism. I believe that you are greatly over stating the influence and impact of post modernism on the contemporary world.
First, I'm not laying all the blame at the foot of postmodernism, I'm suggesting that it's one (important) source of many.
This is most definitely not how you proposed it in the opening post. One of many? The reality is that post modernism is more a product of changing world in a rebellious movement in art and literature than a 'cause' of anything.
In fact, many aspects of post modernism in art and literature has somewhat faded and moderated over time. The over all influence is some what diluted.
As for the rest - well now we've got an actual debate on our hands! Hooray! So let's take one example (feel free to pick on others), multiculturalism. Let's also say for the sake of discussion, that historically, Western secular society has been guilty of colonialism and racism and such. Well first, so have all of today's competing major societal approaches. Second, do you have any examples of approaches that are superior to western secularism? For the record, western secularism has a lot of problems. But I think it's by far the best system we've cooked up so far.
Problem with
bold. How does your egocentric assertion 'best system' equivalent to 'equally valid.' Everybody claims their culture is the best system.
Cultural validity without the egocentric judgement is indeed expressed in the spiritual teaching of the Baha'i Faith.
Well, ah . . . Western Christian Manifest Destiny would be a significant cause of violence in the changing contemporary world, and yes colonialism is major aspect of this and has no competitive comparison in recent history.
I think postmodernism was a major influence on the rise of the idea that all cultures are equally valid.
From what I have read, there is no reference that post modernism claims all cultures are equally valid. Please provide a reference form the perspective of a contemporary post modernist.
Equal is a subjective term in this case, but an unlikely valid value judgement from any pespective. The problem is whether any culture can be considered inherently superior taking away the egocentric perspective that many cultures consider themselves superior. I believe that the claim of inherent superiority of one culture and/or religion is indeed a major cause of the violence in recent history.
You still need to address the following problem:
Your reference makes too much of a broad generalization of 'post modernism' as the 'boggy man' and its supposed impact on society.
It partially cites out of context the reference in the Stanford Encyclopedia of Philosophy. You need to read the whole reference in context.
Postmodernism (Stanford Encyclopedia of Philosophy)