Post-truth Is a Result of Both the Misunderstanding and Rejection of Post-modernism

We find ourselves in a post-truth world because of the poor way in which we have dealt with the revelations of post-modernism.

Post-modernism does indeed say that there is no truth, but that is only part of the story.  Leaving it there is like saying that there is no time because of Einstein's Theory of Relativity. What Einstein said was that time is relative to the speed an object is traveling at, not that time doesn't exist.

The post-modern revelation was that there is no universal and eternal truths because truth is always relative.  That does not mean that truth is completely arbitrary or completely non-existent.

Truth is relative to time and place, which means it is also relative to the past and the perceived or desired future.  Truth is never simple, and it is rarely easy. It is something that needs to be thought out and also believed in, and it must be believable. It needs to resonate with the people (their experience, community, history and vision of the future) and their physical surroundings.

We live in a post-truth world because some people refuse to believe that truth is relative and insist on a solid universal and/or eternal conception of truth and a storehouse of truths that fit that criteria. These people deny the complexity inherent in reality that post-modernism revealed. Others take up only a simplified and naïve version of post-modernism and insist that truth does not exist at all. 

One side insists on using only truths that deny or ignore the importance of context, truths that they know because of their privileged position and abilities. Meanwhile, the other side takes hold of any idea that is beneficial to them and promotes it as a truth.  Sooner or later, the difference between the sides collapses and they both employ each other's tactics. 

As these two sides fight against one another (and take advantage of the average person as they do so) the idea of truth is torn to shreds.  Both sides use it cynically to gain support for their own agenda. As this goes on any truths that we have and need are trivialized and made ineffective.  People, society and knowledge are left in free-fall, or left to wander in a wasteland.  As this goes on society as a whole and the average person loses.