William Stanley Jevons occupies a pivotal position in the history of economic thought, spanning the transition from classical to neo-classical economics and playing a key role in the Marginal Revolution. The breadth of Jevons's work is examined here which: * includes a detailed consideration of a wide range of his work-policy, theoretical, methodological, applied and empirical * relies on textual exegis * takes account of a wide range of secondary sources A new approach to the 'Jevonian revolution' is adopted, which emphasizes the link between poverty and economics and focuses on the nature and meaning of rationality in Jevonian economics.