How does philosophical idealism differ from materialism?

Philosophical idealism and materialism represent opposing metaphysical stances regarding the fundamental nature of reality.

Idealism asserts that reality is essentially mental, spiritual, or conscious in nature. In its most restrictive form, it posits that nothing exists outside of minds and their contents, meaning the material world is either an illusion or entirely dependent on perception. Other versions, such as those proposed by G.W.F. Hegel, suggest that while material things exist, they are fundamentally constituted by or penetrated by "spirit" or mind.123

Materialism, conversely, maintains that the basic substance of the world is matter. It argues that all facts—including those concerning the human mind, will, and history—are causally dependent upon or reducible to physical processes. While idealism seeks to reduce matter to mind, materialism seeks to reduce mind to matter.142

These theories offer competing explanations for the universe:
* Idealism emphasizes that reality is known through mental dimensions and ideas, often arguing that truth is found in the "whole" or the "Absolute".1
* Materialism focuses on physical forms and processes, historically tracing its roots to atomism and the belief that the world consists of physical entities interacting in space.45