Design theory
Design theory is a subfield of design research concerned with various theoretical approaches towards understanding and delineating design principles, design knowledge, and design practice. History. Design theory has been approached and interpreted in many ways, from designers' personal statements of design principles, through constructs of the philosophy of design to a search for a design science. The essay "Ornament and Crime" by Adolf Loos from 1908 is one of the early 'principles' design-theoretical texts. Others include Le Corbusier's "Vers une architecture" (1923), and Victor Papanek's "Design for the real world" (1972). In a 'principles' approach  to design theory, the De Stijl movement (founded in 1917) promoted a geometrical abstract, "ascetic" form of purism that was limited to functionality. This modernist attitude underpinned the Bauhaus movement (1919 onwards). Principles were drawn up for design that were applicable to all areas of modern aesthetics. For an introduction to the philosophy of design see the article by Per Galle at the Royal Danish Academy. An example of early design science was Altshuller's "Theory of inventive problem solving", known as TRIZ, which originated in the Soviet Union in the 1940s. Herbert Simon's 1969 "The sciences of the  artificial" developed further foundations for a science of design. Since then the further development of fields such as design methods, design research, design science and design thinking has promoted a wider understanding of design theory.