Knowledge organization has a rich narrative history as well as a broad philosophical foundation. The story of knowledge organization is complex and fascinating, and it is a long one, with the processes of categorizing and labelling finding their roots in the Biblical tradition, and in the world of classical antiquity. Most knowledge organization enterprises in the ancient and mediaeval period are to do with modelling and making sense of the world; but the principal thread in the narrative really begins in the early modern period, when there was ‘too much to know’, and scholars began to invent means of storing and arranging what they knew about the world. These early knowledge organization systems were there to document, to represent, to describe, and, most importantly, to retrieve information. These functions give us a basis for the modern information sciences of bibliography and knowledge organization, and many features of modern KOS can be traced back to their conceptual origins in the seventeenth century, to the work of Wilkins and the universal language compilers, and to Leibniz and the beginnings of knowledge representation. In the twentieth century many of their ideas can be seen to re-emerge in modern ‘scientific’ KOS, in the theories of Otlet and Ranganathan in particular. The line of succession is very apparent here, and the evolving modern theory of knowledge organization can be seen to develop in the writing of a succession of scholars, all of whom are inter-connected, and who contribute to a mature understanding of knowledge organization in the modern age.