Postmodernism says there’s no such thing as absolute truth - all truth is relative. A postmodernist may argue that truth is an artificial, sociological construct. We’ve demonstrated why that’s not credible.
People inherently understand absolute truth exists - and they conduct their lives accordingly. For example, we know that gravity is an absolute truth and so we don’t step off tall buildings! Even though postmodernism is a prevailing worldview today, it's pretty much impossible to live by in practice.