Though it is not unusual for great philosopher-economists to leave their research project unfinished, the general framework of their thought is not necessarily shrouded in mistery. Smith never wrote the promised theory of justice, but the place it held in his system is clear, as his students’ lecture notes later revealed. By contrast, Mill’s incompleteness seems to be definitive, depending on his longing for something slippery, ill-defined, unattainable. He was unable to accomplish – or refer to the accomplishment of – anything like the ‘science of character’, or ‘ethology’, he aimed at. A similar feeling of incompleteness, bordering on failure, surrounds the work of Alfred Marshall, who dropped the idea of writing the second volume of Principles, though some hints of its planned contents can be gathered from Industry and Trade. This similarity is no surprise, since Marshall was brought up in the atmosphere set by Mill’s scientific and political endeavours (Becattini 1975; Dardi 1984) and shared his problem situation and attitudes towards social issues and social science. In the period when Marshall’s ideas and ideals were taking shape – the late 1860s and early 1870s – the British social scene was still dominated by the need to overcome the nightmare of unhealthy workshops, slums, lack of education and opportunities for betterment which characterized the previous decades and were of major concern to Mill.