Modernism describes both a set of cultural tendencies and an array of associated cultural movements, originally arising from wide-scale and far-reaching changes to Western society in the late nineteenth and early twentieth century. The term encompasses the activities and output of those who felt the "traditional" forms of art, architecture, literature, religious faith, social organization and daily life were becoming outdated in the new economic, social and political conditions of an emerging fully industrialized world.
Modernist architects and designers believed that new technology rendered old styles of building obsolete. Le Corbusier thought that buildings should function as "machines for living in", analogous to cars, which he saw as machines for traveling in. Just as cars had replaced the horse, so modernist design should reject the old styles and structures inherited from Ancient Greece or from the Middle Ages.
Modernist design of houses and furniture also typically emphasized simplicity and clarity of form, open-plan interiors, and the absence of clutter. Modernism reversed the 19th century relationship of public and private: in the 19th century, public buildings were horizontally expansive for a variety of technical reasons, and private buildings emphasized verticality—to fit more private space on more and more limited land. Conversely, in the 20th century, public buildings became vertically oriented, and private buildings became organized horizontally. Many aspects of modernist design still persist within the mainstream of contemporary architecture today, though its previous dogmatism has given way to a more playful use of decoration, historical quotation, and spatial drama.
Modernism is an encompassing label for a wide variety of cultural movements. Postmodernism is essentially a centralized movement that named itself, based on socio-political theory, although the term is now used in a wider sense to refer to activities from the 20th Century onwards which exhibit awareness of and reinterpret the modern. Postmodern theory would assert that the attempt to canonise Modernism "after the fact" is doomed to undisambiguable contradictions. In a narrower sense, what was Modernist was not necessarily also Postmodern. Those elements of Modernism which accentuated the benefits of rationality and socio-technological progress were only Modernist.