Platonic idealism
a general philosophical position deriving both directly and indirectly from the writings of Greek philosopher Plato (c. 427–c. 347 bce), which holds that the phenomena of our world are to be truly known by contemplating them in their ideal forms or abstract essences. Such knowledge is to be achieved by the rational intellect or nous, rather than the senses or the understanding. In The Republic, Plato developed a philosophical system around the central notion that the things of this world are shadows or reflections of their ideal forms existing in a transcendent realm outside time and space (see analogy of the cave). This realm is the “real” world because the forms that comprise it are perfect and eternal, not being subject to change, decay, or limitation like the things of our world. Platonic idealism is essentially a misnomer, as Plato’s doctrine of ideas is actually a form of realism and not of
idealism. This doctrine, the theory of forms, is partly an attempt to solve the logical and other problems involved in relating particulars to universals (e.g., relating blue things to the term blue or good things to the concept goodness); however, it also had a metaphysical or religious dimension, which was later emphasized and extended by Neoplatonism.