The postmodernist movement is a reaction to the ideas of the enlightenment, often referred to as modernity. Basically, it developed in the mid 20th century, largely due to the developments of the 19th and early 20th century. Here's what Wikipedia has to say about Postmodernism.
While postmodernist thought is far from perfect, it does raise good points. Here are a few valid claims postmodernists make:
Even though they raise valid concerns, postmodernist thinkers make mistakes. These are a few places postmodernism goes wrong:
In order to correct Postmodernism, we have to look at the core of it. The main issue I find is that it is concerned with things that exist, but they over-emphasize them or lend too much credence to those facets of their philosophy. For instance, there are power structures that influence our world. However, the way postmodernists look for these structures in every nook and cranny of human culture is disordered.
It also holds contradicting ideas like the universal truths of power structures and hierarchies alongside ideas of radical self-referentiality. Lastly, I judge a philosophy by it's fruits, and the fields that have been influenced by postmodernism have been corrupted. Many are hardly intelligible at this point.