Postmodernism can be seen as a reaction against the ideas and values of Modernism. The term is linked to scepticism, irony and critiques against universal truths and undisputable reality.

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The origins of Postmodernism
This word was first used around 1970. Postmodernism was a reaction against modernism. While modernism was focused on idealism and reason, postmodernism resulted from scepticism and doubts about reason. It fought against the notion that there are universal certainties. Postmodern art was based on philosophy of the twentieth century, and thought that individual experience and interpretation of our experience was more important than abstract concepts.

Image source: https://www.tate.org.uk/art/art-terms/f/formalism
Post Modern Architecture
The origins can be traced back to Robert Venturi’s book “Complexity and Contradiction in Architecture”. There’s a revival of traditional features and methods. Post modernists were influenced by past architecture and classical designs were used in new ways just to send a message to the modernist people.

Robert Charles Venturi, Jr. put together his ideas in “Complexity and Contradiction“ and could be seen in his earliest concepts, including his first major work, the Guild House created with a feeling of artistic tension, fusing high-art aesthetics with motifs taken from popular culture. One of his main works, the Franklin Court is located near to the site of Benjamin Franklin’s residence. Because no historical certainties of the look of the exterior remain, the space remaining is marked by a wonderful, massive “Ghost Structure” designed by Robert Venturi.
Image source: https://www.archdaily.com.br/br/photographer/frank-hanswijk
The two “ghost structures” made of square tubular steel, give an idea of the outline of the old demolished structures into the courtyard. The design is the result of inadequate historical guidelines to restore the structures the correct way.

Image source: https://en.wikipedia.org/wiki/Franklin_Court

Charles Moore was an American architect, whose most known work is the Piazza d’Italia in New Orleans. Both a memorial and a public place, the piazza, is a manifestation of Moore’s ideas of an inclusive architecture, able to speak and be enjoyed by anyone. Moore’s art, however, immediately attracted fans and detractors, and many thought that his architectural populism was kitsch.
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Post Modern Furniture
Post-modern furniture, as architecture, is a reaction against modernism. No piece of furniture embodies all the features of this new furniture, but as a whole, the furniture puts together several concerns. Much of it are inspired to classical forms, and are figurative rather than abstract. This furnishing is often adorned and usually made of wood, painted or left natural.

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Info source: https://en.wikipedia.org/wiki/Postmodern_art