Postmodernists assume that there are no standards for truth, beauty, or goodness. The wording of a text is less important than the reader's interpretation of the text. The reader's subjective interpretation determines what the author intended.
They believe that no matter how a writer constructs a sentence, it can never tell us about the real world, but only about the world as understood by the reader. By allowing the reader to invent new meanings, the text is freed from the tyranny of the author's single intended meaning.
"Critical theory" navel-gazing at its finest.