It's time for some plain talk.
Humans are not truth-seekers, and never were. For our purposes here, humans are story-telling social animals. There is no relationship between telling stories and having an affinity for "objective" truth in so far was we can determine it. Story-telling is subjective by definition.
By the way, I have no evolutionary "just-so" story to tell which purports to explain why humans are story-telling social animals. Close and repeated observation tells us so. (See 2016 in America.) The fact that humans are deluded about what they are does not change those observations.
In particular, and in the cases I'm interested in, humans have no natural affinity for truth (reality) when when there is something important at stake. First, what does "important" mean in this context?
Something important is at stake when instinctual drives are in play, especially when there are conflicts with instinctual drives. For example, there may threats to group or individual psychological coherence (existential threats). Or the social distribution of status and power is on the line (These two examples are not mutually exclusive).
It is clear that there is always something important at stake in politics (in-group cooperation, elites versus out-groups, inter-group conflict). Politics is far more pervasive in human social interaction than you might think.
When something important is at stake, you get bullshit. You get self-serving stories. I will quote from the third Flatland essay, which I wrote in 2014. Bullshit is ubiquitous in human life. I wrote that essay in part to answer the question why is there so much bullshit?
In the Flatland model, bullshitting is not some random phenomenon; it is characteristic human behavior. There is more bullshit now (at least in absolute terms) than there used to be because there are so many more people than there used to be. Moreover, thanks to huge advances in communications technology, all these people have a much greater ability to express themselves in public and find an audience for their nonsense. Spin is ubiquitous in modern life because there are far more bullshitting opportunities clamoring for our attention...
In individuals or social groups, bullshit, or spin, is a self-serving post-hoc rationalization of some unconscious motivation. Bullshit arises when there is an unconscious need to—
(1) maintain a positive self-image or manage positive impressions of the self by others;
(2) deflect existential threats to the self or group; or
(3) advance the agenda of the bullshitter (representing himself or the group).
This list is not meant to be exhaustive, nor are these needs mutually exclusive.
Bullshit stands opposed to a reasoned, objective search for truth. Spin often departs from reality in a serious way, or, more commonly, contains "half-truths" which advance the agenda of the bullshitter. Otherwise, if speech or writing does not depart from reality by the 1) assertion of falsehoods or 2) omission of crucial facts, even when unconscious motivations exist—unconscious motivations always exist—the discourse in question is not bullshit.
Of course, not everything humans say or write is bullshit. It is clear that humans do sometimes reason without an ax to grind or some easily identifiable agenda, although it is also clear that unfettered rationality is far rarer than commonly assumed. In short, bullshit arises when there is something important at stake, just as "bad news" filtering does...
Repeating myself, if this model is correct, we can not be in the "post-truth" era because there was never a time when humans had a positive relationship with truth which can deteriorate at critical times in human history (like now in the United States).
That said, there are degrees of bullshit. When social groups become very politically polarized, as they have in the United States over the last 40 years, the orthogonal relationship which story-telling humans have with truth can indeed deteriorate. But in terms of characteristic bullshit, this distinction isn't very important. Lately, in the alleged "post-truth" era, it amounts to the difference between fake news—humans making shit up with no factual basis at all—and "real" news as served up by the mainstream media. I'll repeat this from above for your convenience.
Spin often departs from reality in a serious way, or, more commonly, contains "half-truths" which advance the agenda of the bullshitter.
Fake news is the former; "real" news from the New York Times is the latter. News with "half-truths" omits those parts of the truth which don't align with the story being told. Other techniques include using anonymous but "expert" sources who themselves have an ax to grind, or making misleading statements which slant the story one way and not another.
It's also clear enough that humans have little or no interest in the "facts" in so far as fake news is just as engaging on social media as "real" news (if not more so, and follow the link above).
You get these kinds of disputes because humans labor under the delusion that truth matters to them. It doesn't. Only stories matter. Derisive laughter is the only appropriate response when politically biased "news explainers" at Vox tell you how much truth matters. Such examples can be repeated ad infinitum.
And one more thing. It was the internet which made it possible to understand that humans generally behave this way. Never before had it been possible to observe human behavior on such a large scale. And what was the result?
Digital technology has blessed us with better ways to capture and disseminate news. There are cameras and audio recorders everywhere, and as soon as something happens, you can find primary proof of it online.
You would think that greater primary documentation would lead to a better cultural agreement about the “truth.” In fact, the opposite has happened.
Consider the difference in the examples of the John F. Kennedy assassination and 9/11. While you’ve probably seen only a single film clip of the scene from Dealey Plaza in 1963 when President Kennedy was shot, hundreds of television and amateur cameras were pointed at the scene on 9/11. Yet neither issue is settled for Americans; in one recent survey, about as many people said the government was concealing the truth about 9/11 as those who said the same about the Kennedy assassination.
Documentary proof seems to have lost its power...
This gets to the deeper problem: We all tend to filter documentary evidence through our own biases.
Researchers have shown that two people with differing points of view can look at the same picture, video or document and come away with strikingly different ideas about what it shows.
That dynamic has played out repeatedly this year. Some people look at the WikiLeaks revelations about Mrs. Clinton’s campaign and see a smoking gun, while others say it’s no big deal, and that besides, it’s been doctored or stolen or taken out of context. Surveys show that people who liked Mr. Trump saw the Access Hollywood tape where he casually referenced groping women as mere “locker room talk”; those who didn’t like him considered it the worst thing in the world.
There are now entire sites whose only mission is to publish outrageous, completely fake news online (like real news, fake news has become a business). Partisan Facebook pages have gotten into the act; a recent BuzzFeed analysis of top political pages on Facebook showed that right-wing sites published false or misleading information 38 percent of the time, and lefty sites did so 20 percent of the time.
“Where hoaxes before were shared by your great-aunt who didn’t understand the internet, the misinformation that circulates online is now being reinforced by political campaigns, by political candidates or by amorphous groups of tweeters working around the campaigns,” said Caitlin Dewey, a reporter at The Washington Post who once wrote a column called “What Was Fake on the Internet This Week.”
Ms. Dewey’s column began in 2014, but by the end of last year, she decided to hang up her fact-checking hat because she had doubts that she was convincing anyone.
“In many ways the debunking just reinforced the sense of alienation or outrage that people feel about the topic, and ultimately you’ve done more harm than good,” she said.
Caitlin Dewey correctly concluded that debunking fake news was probably doing more harm than good.
Welcome to your world.