In a new essay, Martin Gurri writes,

Post-truth, as I define it, signifies a moment of sharply divergent perspectives on every subject or event, without a trusted authority in the room to settle the matter. A telling symptom is that we no longer care to persuade. We aim to impose our facts and annihilate theirs, a process closer to intellectual holy war than to critical thinking.

He and I are going to try to do a podcast on the topic, since I have also been interested in it.