What is Idealism?
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 this is from msn encarta.
Basically, Idealism is a group of concepts in philosophy asserting that reality and existence is dependent upon the Mind, specifically the immaterial mentality of oneself. There are numerous variations and distinct subcategories of Idealism, however, such as epistemic skepticism, classical idealism, subjective and objective idealism, transcendental idealism, and even René Descartes' concept of solipsism. Idealism is a key aspect of religious beliefs, especially in regards to the supernatural. Idealism is contrary to philosophical materialism, among other concepts and theories.