After the restoration of the monarchy in 1660, a group of Britons began to apply quantitative analysis to policy. This they called 'political arithmetic'. Applying mathematical method to the study of the practical problems of statecraft and commerce, they made extensive use of observed data and pioneered the use of actuarial tables. This study explores to what extent they owed their ideas to Francis Bacon, Thomas Hobbes, etc; and whether they did indeed use Baconian method.