This thesis attempts to elucidate the relationship between science and beauty by examining theories of proportion in art and architecture from the 16th to the 20th century. It follows the hypothesis that these theories reflect the intellectual conflict between phenomena and spirit (or sense and substance, appearance and essence) as postulated by Eric Voegelin as the result of the rise of modern mathematics and physics since the second half of the 16th century , leading ultimately to "scientism" (or the bias accorded to the mathematized study of natural phenomena as the only means of comprehending reality, even to the extreme of denying the reality of spiritual substance itself) in the 19th century. It begins by reviewing the concept of proportion (a word translated by Cicero from the Greek analogial since its transformation from Greek philosophy to the Vitruvian interpretations, and continues with exposition of the major theoreticians since the 16th century, divulging connections of the problem with various scientific (or pseudo-scientific) practices which include anatomy, astrology, physiognomy, science of expression, craniometry, biological morphology, statistics and music. The thesis also tries to situate these work within the main-stream theoretical debates in art and architecture, exploring their significance in the philosophical shaping of the concepts of decorum, character, taste and eventually the 'science' of aesthetics. It illustrates in its entirety, therefore, the evolution of the struggle over the question whether a science of beauty )i': .',r. is possible with regard to proportion, which might serve to explain not only the crisis condition in art and architecture at present (the fact that some of these proportional theories were determined by human or natural scientists in the 18th and 19th century rather than artists and architects is evidence of this crisis) but would contribute also to the understanding of the history of human civilisation put at peril by scientism.