 The diversity of explanatory roles assigned to attention in the eighteenth and nineteenth centuries meant that theorizing about attention at the end of the nineteenth century was in a chaotic state. The ambition for theorists of attention writing at the end of the nineteenth and the beginning of the twentieth centuries was to get this chaos into order. The theories of attention proposed in this period therefore tended to take the form of attempts to reveal attention as something less mysterious and less complex than earlier writers had supposed. This ambition to give a ‘nothing but…’ reduction of attention can be seen in the most influential work from this period: William James’ The Principles of Psychology (1890).