A significant but seldom explored feature of social change brought about by popular education in the modern period lies in its intimate and complex association with the humanizing idea of the "lifelong". At a moment when the idea of "lifelong learning" exercises a considerable policy influence, it is perhaps timely to reflect on the relation of education with the "lifelong" in an explicitly historical way. In this paper, the notion of this concept is seen to exert an immensely attractive but fundamentally unstable influence over educational activity. Across time, its hegemonic potential may be seen to be readily available to one or other of the two sides of the act of education--teaching and learning--but seldom to both simultaneously. The paper traces a historical trajectory which describes the eclipse of nineteenth-century lifelong learning in terms of an intellectual migration towards lifelong teaching in the twentieth century. At the end of that century and into the twenty-first, we see that a new incarnation of lifelong learning has been paralleled by the decline of a century-long tradition of teaching as the guardian of the "lifelong" in education. (Contains 4 figures and 69 footnotes.)