FOREWORD interest in the development of European architecture, and every- thing that is not European or—as I thus propose using the term European—Western in character. For Western civilisation is a dis- tinct unit, a biological unit, one is tempted to say. Not for racial reasons certainly—it is shallow materialism to assume that—but for cultural reasons. Which nations make up Western civilisation at any given moment, at what juncture a nation enters it, at what juncture a nation ceases to be of it—such questions are for the individual historian to decide. Nor can he expect his decision to be universally accepted. The cause of this uncertainty regarding historical categories is obvious enough. Though a civilisation may appear entirely clear in its essential characteristics when we thinlr of its highest achieve- ments, it seems blurred and hazy when we try to focus its exact out- lines in time and space. Taking Western civilisation, it is certain that prehistory is not part of it, as the prehistory of every civilisation—the word expresses it—is a stage prce, i.e. before that civilisation itself is born. The birth of a civilisation coincides with the moment when a leading idea, a leitmotiv, emerges for the first time, the idea which will in the course of the centuries to follow gather strength, spread, mature, mellow, and ultimately—this is fate, and must be faced—abandon the civilisa- tion whose soul it had been. When this happens, the civilisation dies, and another, somewhere else or from the same soil, grows up, starting out of its own prehistory into its own primitive dark age, and then developing its own essentially new ideology. Thus it was, to recall only the most familiar example, when the Roman Empire died, and Western civilisation was born out of prehistoric darkness, passed through its Merovingian infancy, and then took shape first under Charlemagne and finally during die reign of Otto the Great in the loth century. Now, besides prehistory and Antiquity, nearly all that belongs to the first thousand years A.D. has had to be left out, because the events of that age, centred in the Eastern Mediterranean—i.e. the oriental- isation of die Roman Empire, early Christianity, early Talmudism, early Mohammedanism and the Byzantine Empire, widi its successor civilisations in the Balkans and Russia—make up a separate civilisa- tion of its own, of a character fundamentally different from the Greek and Roman as well as the Western. So diese diree omissions—all omissions in time—will, it is to be hoped, be considered justifiable. As for limitations in space, a few xvii"