An encounter with the architectural ideas of the past few centuries is a little like rushing upon a sleeping Proteus – the mythical sea god and herdsman of seals who (to Odysseus) had the power to take all manners of shapes. One has to hold on fast as theory evolves through its many guises until at last it is forced to reveal its true identity. In the seventeenth century, it was codified and was more or less restricted to one or two academies; its main ideas were expounded through lectures and treatises. During the Enlightenment, it steps out into the public forum for the first time, and nonacademic viewpoints begin to challenge accepted academic dogmas. The rise of national identities and the availability of architectural journals in the nineteenth century vastly expanded and facilitated theoretical discourse. And of course the manifestos of the twentieth century were usually short, minimalist polemical statements, sometimes cogently reduced to axiomatic diagrams or simple sketches. We shall take architectural theory in its broadest sense and define it simply as the history of architectural ideas, literary or otherwise. Further, as every generation possesses the need to define itself in relation to what exists, architectural theory has almost always been a reaction to the past.

The present work seeks to narrate the main lines of modern architectural thought from 1673 to the troubling year of 1968. These dates may appear arbitrary, but they have a foundation. These dates may appear arbitrary, but they have a foundation. To start with, the words theory and modern both first came into prominence in the late seventeenth century.