The postmodern novel attempts to move away from and beyond the premise of the modern novel.
Whereas the modern novel focuses on reason and scientific discovery as the most important basis of life and opinion, postmodernism does not accept that reason and science are sufficient to achieve an understanding of life and the world. This conception is based on discoveries such as Relativity, the Uncertainty Principle, and quantum physics. The basic principle of the movement is the belief that reason alone cannot provide an explanation for these discoveries.
While the modern novel therefore relies on realism and logic in the narrative structure, postmodernist novels seek to convey that reality is unknowable and inaccessible through language, and even may not exist at all.