The origins of sociological science are traced back to England in the second half of the seventeenth century and in particular to the contributions made by John Graunt and Edmond Halley. Their work is distinguished from the political arithmetic of William Petty in having a more general concern with population regularities and in being based on ‘reasoning with numbers’ of a more advanced kind. Graunt’s Natural and Political Observations Made upon the Bills of Mortality is a pioneering analysis of social data in numerical form and characterised by a remarkably scientific attitude. Halley’s life-table represents the first application to such social data of elements of modern probability theory. Unfortunately, little was done to build on their work until the early nineteenth century.