Schopenhauer's criticism of the Kantian philosophy

Schopenhauer's criticism of Kantian philosophy is that he thought Kant's theories were too complicated. He believed that the way Kant tried to understand philosophical questions was too difficult to understand and he felt that the ideas were too abstract. He thought that a simpler way was needed to understand important questions about the world. He also believed that Kant was too certain of certain universal moral laws, which Schopenhauer thought were impossible to know for certain. So, Schopenhauer was criticizing Kant for thinking that he knew things for certain that he couldn't possibly know for sure.