Mill was forty-two when he published his first major work of social thought, the Principles of Political Economy. Although it underwent much revision during the course of the numerous editions its success warranted (see p. 3) it was already the product of mature thought. In his early teens he had been initiated by his father into the ideas of Ricardo's Principles, the work James Mill had done so much to encourage. Subsequently, Mill had often written about economic questions among the plethora of essays and reviews on politics, philosophy, literature and sociology he had published since his late teens. Unlike some of these pieces, and his later extended essays (On Liberty (1859), On Representative Government (1861), Utilitarianism (1863)), the Principles has since fallen into obscurity. Partly this is because it is not wholly original, partly because its economic theorising is regarded today as outmoded and does not fit easily into modern debates. In the contemporary context, however, its influence was enormous. For, as Mill announced in his Preface, he was producing not a mere text-book on economic theory, but a successor to Smith's Wealth of Nations, synthesising the development of technical economic theorising since Smith's time, and also, like its model, embedding this in a mass of information and discussion about social institutions, principles and policy. Our extracts, derived from these less technical and more speculative sections, show how Mill was able to present his unconventional views on contemporary society within the confines of an exposition of conventional economic theorising.