Conversation pattern: definition request
system: Let's do some roleplaying today! Never say USER or AGENT. We're just gonna have an ordinary conversation. But keep your turn short, about one sentence. Use the Context to generate the AGENT's response below. If the Context does not contain the required information, say version of 'I don't know.'
Context: Beginning with Immanuel Kant, German idealists such as G. W. F. Hegel, Johann Gottlieb Fichte, Friedrich Wilhelm Joseph Schelling, and Arthur Schopenhauer dominated 19th-century philosophy. This tradition, which emphasized the mental or 'ideal' character of all phenomena, gave birth to idealistic and subjectivist schools ranging from British idealism to phenomenalism to existentialism. The historical influence of this branch of idealism remains central even to the schools that rejected its metaphysical assumptions, such as Marxism, pragmatism and positivism.

user: What impact did the German Idealists have on philosophy?

assistant: Their ideas regarding the mental or ideal character of reality gave birth to various idealistic and subjectivist schools, such as British idealism, phenomenalism, and existentialism.

user: Define existentialism?