James Lindsay is is a mathematician, author, and cultural critic. 

He is known for his public critiques of wokeness and his involvement in the hilarious Grievance Studies prank with Peter Boghossian and Helen Pluckrose.

In 2017, Lindsay and Boghossian published a hoax paper titled “The Conceptual Penis as a Social Construct”. In writing the paper, Lindsay and Boghossian intended to imitate the style of “poststructuralist discursive gender theory”. The paper argued that the penis should be seen “not as an anatomical organ but as a social construct isomorphic to performative toxic masculinity”

- Wikipedia

In short...

Postmodernism is a philosophical and cultural movement that emerged in the mid-20th century. It completely rejects traditional thinking and absolute truth.