Hannah Arendt and Jean-Jacques Rousseau, though separated by more than two centuries, were nonetheless immersed in periods of remarkable societal change. Both epochs were driven in many ways by science, which brought irreversible transformation to the ways that humans ordered and sustained themselves. The nature of the human being participant in these upheavals, however, remained constant. The individual was forced to adapt an old constitution to new roles and relationships to society. As early as 1750, observers of such developments began to examine them critically, to interrogate the changes that will be wrought on mankind. The dangers they posed, in concert with unimaginable capabilities, should be noted well if we are to carry them into a better world.