Idealism: doctrine according to which the objects of external perception ultimately consist of or express ideas.
In philosophy, not a moral or political category, but one to denote an onto-axiological system which holds ideas to be primary in explaining the world/cosmos, knowledge and value. Idealism is the longest reigning tendency in philosophy, with many philosophical schools from Plato on, normally opposed to Materialism.
A long-dominant tendency of Western and Eastern philosophy of various schools to posit ideas as prior to matter on ontological, epistemological and value planes. Usually contrasted to Materialism.
See also Platonic and Universals.