In recent years sociological work in the field of stratification and social mobility has become, in at least one sense of the term, impressively cosmopolitan. National sample surveys which include data on inter-generational occupational mobility have been carried out in every major Western nation and in a good many non-Western societies as well, and those have inspired some ambitious comparative analyses of social mobility. This development, as S. M. Miller puts it, has had the virtue of making "the study of mobility one of the few fields of sociology which has overcome national parochialisms”. True as this is, however, it must be said that there are forms of parochialism other than national. Much contemporary research into social mobility suffers from one of these - a parochialism of time rather than of place, as it were, the parochialism of presentism. My purpose here is to suggest what is lost as a result of that parochialism, and to argue that a sense of the past, an ability to see his subject in historical depth, is not a luxury but a necessity for the student of social mobility.