The ten essays in this special issue of Science in Context address the formation of scientific personae from the sixteenth through the twentieth centuries in Europe and North America. The departure point for the collection was a year-long (1998-99) research project (including a final conference) on "The Scientific Persona" organized at the Max Planck Institute for the History of Science, Berlin. This project was in turn inspired by a seminal essay by the French anthropologist Marcel Mauss on the historical and cultural development of the category of personhood, from the tribal personnage to the modern moi (Mauss 1938). Because the application of Mauss' term "persona" to the history of science is somewhat novel, and also unforeseen by Mauss himself, we must first explain what is meant by the term in these essays, and why we believe Mauss' historicization of personhood, somewhat modified, to be illuminating for the history of science. Mauss' essay, "Une catégorie de l'esprit humain: La notion de personne, celle de 'moi'. Un plan de travail," originally delivered in 1938 as the Huxley Memorial Lecture in London, reveals its program already in its title: it was meant to present British colleagues with an example of the "French School of Sociology," more particularly "the social history of the categories of the human mind" (Mauss 1938, 263). Mauss wished to display the possibilities of this historicized neo-Kantianism by means of a prototypical Kantian example, the self, das Ich (Trendelenberg 1908), assumed by modern philosophers to be an innate mental category. To this end, he traced a long developmental arc from the rites of personnage in ancient Greece, Rome, and India (which he believed to be to some degree paralleled by extant practices among the indigenous peoples of North America and Australia), through the institutions of Roman law and medieval Christian theology that forged the persona, to the eighteenth-century emergence in a few European cultures of the moi or self. Mauss' three phases might roughly (the word is used advisedly-he insisted upon the crudeness of his first approximations) be characterized as follows. In societies organized around the personnage, or "role," identities and the names that designate them are recycled from generation to generation, so that ancestors are endlessly reincarnated and the social structure of the clan appears static. These reincarnations are often reinforced by inherited names, ranks, rights, and functions, and symbolized by ceremonies involving masks to map the individual face into the ancestral role. The Latin word persona in fact means "mask," and Mauss located the critical transitional phase between personnage and moi in Greek and Latin moral philosophy and law, later