How would you define the Postmodern worldview?
The Postmodern worldview is the ultimate result of Modernism, which in turn traces to the Enlightenment. Connecting these three is a common metaphysics that separates subject from object in a way that does two things: 1) Keeps the subject from knowing things "in themselves" (objects), and 2) Pushes the subject to create its own reality. After all, a subject that cannot truly know an object still needs to function, and to function it needs a reality. If "real" reality is out of reach because the world of appearances is just a representation of something we cannot know (as it is in mainstream metaphysics), then the subject must make up a reality. So, the Enlightenment project that stretched from Descartes to Kant gave us a subject that was at one and the same time crippled (unable to know actual reality) and godlike (empowered to create its own reality). At first, this issued in "objective" science, which examined the world as measurable and observable, though not strictly "knowable." In the arts, this resulted at length in abstract art, serial music, and other "objective" art forms. This was Modernism. After a while, a reaction to this "objective" side of the object-subject split gave us wholly subjective art, such as minimalism and eclectic architecture. Postmodernism may seem to be the opposite of Modernism, but it merely explores the godlike side of the subject, whimsical and unconcerned with form, creating "realities" without any meaning beyond themselves; whereas Modernism, with its strict adherence to form and to representational qualities such as unity and balance, acknowledged a distant, measurable, "objective" world ultimately unknowable by the epistemologically crippled subject. This cycle will repeat until the old metaphysics of "subject-object" is replaced with a different ontological vision. (Please note: Mine is not a generally accepted view.)
I would define it as an argued subjectivity.
It can be argued, but there is no objective data showing that it is not self-refuting.
It is an abandonment of logic, which proposes that each person has their individual and personal truth or "narrative".
To justify Postmodernist Thought, an advocate for that worldview needs to abandon the logical exercise of Reductio ad absurdum.
In other words, by Socratic Method, an advocate of Postmodernist Thought would have to be able to show that their "narrative" transcends the laws which govern my reality.
The Postmodernist can propose that their "narrative" for truth includes transcending known natural laws, whereas my "narrative" does not include transcending known natural laws.
The Postmodernist can include such unscientific premises as belief in Rhonda Byrne's Law of Attraction whereas I cannot justify such an unscientific idea as my own premise. Based upon logical functioning, such as using Reductio ad absurdum, I can recognize that regardless of my "narrative" I am still subject to natural law.
The advocate for Postmodernist Thought can assert a personal narrative which excludes limitations in the context of natural law.
As the blatant opposition to the Modernist worldview.
What would Modernism be portrayed by in this day and age? I would say that the idealisation of society as an utopia where there are very limited problems, war and famine does not exist and technology has helped us reach an overall global state of well-being, be it in health, finance, society and so on. This ideology yearns for the ‘good old days' in a more present setting.
Postmodernism yells ‘Bullshit' at that. It completely denies that the ‘good old days' even existed, or at least portray them in a more realistic, less romanticised fashion (which almost always ends up being a demonstration of a shittier world with a couple of salvageable aspects). Post-modern ideology states a grimmer view on the state of things. It is not nihilism, since it does yearn for a better living, but it doesn't like to compare; it knows there is a way to achieve the goals it strives for, but it doesn't idealise, doesn't set fantastic standards and tends to point out everything that is wrong in the world.
War exists, famine exists, we're nowhere near to ending disease, not on a physical nor on the emotional or mental levels; technology is good and all but it's ways away from being ideal to constitute a viable solution to even half of our problems. The world my grandparents talk about, the old days were filled with wars, rape and murder, slavery and denial of basic human rights. We need not put the past in a pedestal nor wait for a magical solution to all, we need to work to make the world marginally better each day.
That there is no single narrative of progress.
Therefore something is only true when it is converged upon from multiple points of view.
In Folklore we might say, there is no hegemonic expression of culture which represents the entire culture.
In Postmodern culture, rather than being defined by a single culture, most of us tend to belong to multiple overlapping subcultures.
Some of which might even conflict with each other.
Many of us are multi-literate with respect to different subcultures yet there is no common culture in which to express them all.
Or even most of them.