Twentieth-century Rationalism derived less from a special, unified theoretical work than from a common belief that the most varied problems posed by the real world could be resolved by reason. In that respect it represented a reaction to historicism and a contrast to Art Nouveau and Expressionism.
The French Louis XVI style (better known as neoclassicism) emerged in the mid-18th century with its roots in the waning interest of the Baroque period. The architectural notions of the time gravitated more and more to the belief that reason and natural forms are tied closely together, and that the rationality of science should serve as the basis for where structural members should be placed. Towards the end of the 18th century, Jean-Nicolas-Louis Durand, a teacher at the influential École Polytechnique in Paris at the time, argued that architecture in its entirety was based in science.
Architects such as Henri Labrouste and Auguste Perret incorporated the virtues of structural rationalism throughout the 19th century in their buildings. By the early 20th century, architects such as Hendrik Petrus Berlage were exploring the idea that structure itself could create space without the need for decoration. This gave rise to modernism, which further explored this concept. More specifically, the Soviet Modernist group ASNOVA were known as 'the Rationalists'.