How does idealism challenge the view that material things exist independently of the mind?

Idealism challenges the view that material things exist independently of the mind by asserting that reality is fundamentally mental or spiritual in nature. Rather than accepting that objects possess an existence outside of consciousness, idealists argue that what we perceive as the material world is either composed of ideas or is conditioned by the mind’s processes.12

The most direct challenge comes from subjective idealism, famously championed by George Berkeley. Berkeley argued that "to be is to be perceived" (esse est percipi). He contended that qualities we attribute to objects—such as extension, hardness, or color—are merely sense perceptions that cannot exist without a subject to perceive them. Because all knowledge is derived from perception, he rejected the existence of an imperceptible material "substrate" that supposedly supports these qualities.342

Other forms of idealism, such as those proposed by G.W.F. Hegel, suggest that while material things may have a form of reality, they are ultimately constituted by or penetrated by "spirit" or mind. Consequently, idealism posits that the external world is not an independent, objective reality, but is instead fundamentally linked to the existence of minds.531