The research for this study started in 1972, when I was a graduate student at the Scuola Normale Superiore of Pisa. In 1973, a Lord Florey European Studentship at the Queen's College, Oxford gave new impulse to my work. I was then able to exploit the resources of the Bodleian Library, the manuscript collections of several Colleges – Oriel and Manchester in particular – and of Pusey House. Mr Francis Baden Powell kindly put at my disposal the important collection of papers in his possession. I also enjoyed the hospitality of the Wellcome Unit for the History of Medicine, and I greatly profited from the advice of Dr Charles Webster, its Director.

The first draft of this monograph was submitted in August 1980 to the History Faculty at Oxford University in the form of a D.Phil, dissertation. Further research on early nineteenth-century English philosophy of science, with particular reference to the debates on the epistemological status of theories in political economy, was undertaken at King's College, Cambridge, where I served as Senior Research Associate during the academic year 1980–1. I enjoyed there the comradeship and intellectual stimulation of the members of the Research Centre engaged in the ‘Political economy and society, 1750–1850’ project.

The years 1981–3 were spent deepening my understanding of the early history of evolutionary ideas in France and England. The resources of the National Library of Florence were particularly relevant for the revision of the fourth part of the present study. Pietro Omodeo, a pioneer of contemporary studies of Lamarck and French science in the early nineteenth century has offered constant advice and encouragement.