Given the task definition and input, reply with output. In this task, we ask you to rewrite a sentence in simple English without changing its general meaning. Essentially, you want to make the sentence easier to read by using simpler words, utilizing more straightforward sentence structures, and omitting non-essential information etc.

German idealism ( also known as post-Kantian idealism , post-Kantian philosophy , or simply post-Kantianism ) was a philosophical movement that emerged in Germany in the late 18th and early 19th centuries .
German idealism is a group of theories in philosophy that began in Germany in the late eighteenth and early nineteenth centuries .