Western painting seems to have changed more radically this century than at any other time during its history and this is due in considerable measure to the development of abstraction. For the essence of truly abstract art appears to be its use of the pure elements of the medium — line, shape and colour — for purposes which have nothing to do with representation. In this respect abstract art seems to stand in marked contrast to figurative depiction and the creation of an illusion of objects in three-dimensional space which are virtually defining characteristics of pre-20th century art.