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How do realism and idealism differ over whether reality exists independently of the mind?

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Marble bust of Aristotle with a beard and draped robe, showing detailed facial features and wavy hair, set against a dark background. — metaphysics Detail of a Roman copy (2nd century bce) of a Greek alabaster portrait bust of Aristotle (c. 325 bce); in the collection of the Museo Nazionale Romano, Rome.

In the context of metaphysics, the fundamental disagreement between realism and idealism centers on whether reality possesses an existence independent of the human mind.123

Realism maintains that the objects of our knowledge, belief, and experience—such as the external world—possess an existence and nature that remain the same whether or not anyone is thinking about or perceiving them. For the realist, human cognition aims to grasp these objects as they truly are, existing outside and independently of the mind.432

Idealism challenges this by asserting that reality is fundamentally mental or spiritual in nature. In its most restrictive form, idealism claims that there is nothing in reality other than ideas and the minds that hold them. Consequently, idealists often argue that objects are conditioned by their perceptibility, famously summarized by the doctrine esse est percipi ("to be is to be perceived"). While some versions, such as Immanuel Kant’s transcendental idealism, attempt to reconcile the existence of external objects with the mind's role in shaping experience, the core idealist tension remains the rejection of a reality that exists entirely "behind" or apart from mental representation.215