I.

Introduction

Idealism, in philosophy, a theory of reality and of knowledge that attributes to consciousness, or the immaterial mind, a primary role in the constitution of the world. More narrowly, within metaphysics, idealism is the view that all physical objects are mind-dependent and can have no existence apart from a mind that is conscious of them. This view is contrasted with materialism, which maintains that consciousness itself is reducible to purely physical elements and processes—thus, according to the materialistic view, the world is entirely mind-independent, composed only of physical objects and physical interactions. In epistemology, idealism is opposed to realism, the view that mind-independent physical objects exist that can be known through the senses. Metaphysical realism has traditionally led to epistemological skepticism, the doctrine that knowledge of reality is impossible, and has thereby provided an important motivation for theories of idealism, which contend that reality is mind-dependent and that true knowledge of reality is gained by relying upon a spiritual or conscious source.