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),[1] 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.
For an introduction to the philosophy of design see the article by Per Galle[2] 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.