This book does two things. First, it defines and explores the idea of modernity, returning it to its historical context and showing how theory and practice in the modern visual arts emerged over three centuries. Concepts central to the meaning of modernity will be explained, including: style, modernization, progress, ideology and universality. Movements across all disciplines from the Enlightenment onwards will be discussed, including: Neoclassicism, Romanticism, the Design Reform movement, Realism, Impressionism, Art Nouveau, NeoImpressionism, the Arts and Crafts movement, Cubism, Futurism, De Stijl, the International Style, Surrealism, Pop, Minimalism, Conceptualism and Postmodernism. Second, the book explores the rise of idealism in the modern visual arts. The attempt to create a definitive, positive style, that was capable of transforming not only art but society as a whole, became the obsessive quest of succeeding generations of artists, architects and designers. This secular Utopianism had particular recurring features. By far the most important of these was the concept of simplicity. Simplicity underpinned successive generations of idealist art and design; during the twentieth century - reinvented as purity - it reached a definitive pitch, becoming the core idea underlying humanist aesthetics. By 1970, the International Style in architecture and design and various forms of minimal abstraction in the fine arts had come to dominate world art. The rise and collapse of this unfolding are here described in detail.