The eighteenth century was to be the age of the Enlightenment, but already before the seventeenth century had closed the prototypes of all the weapons in its armoury had been created and tested. Of the new thought of the seventeenth century Paul Hazard has written, ‘Total, imperious and profound, it prepared in its turn, even before the seventeenth century was completed, almost the whole of the eighteenth century.’ The great battle of ideas took place before 1715, and even before 1700.

Religion was the main citadel of orthodox thought, and the grand strategy of the attack on it had already been laid down by the English deists before 1715. A handful of extremists, such as Anthony Collins, moved beyond deism and repudiated religion altogether; but the latitudinarian divines of the Church of England had themselves gone so far towards the acceptance of rational religion that the deistic controversy died down in England for lack of opposition. Meanwhile the deistic and free-thinking writings of England were being introduced into France, where they were to acquire a new lease of life. Though French writers in the first half of the century handled the subject of religion with caution, their treatment concealed a more deep-seated hostility than existed across the Channel. When deism emerged into the open in France with the writings of Voltaire and the Encyclopédistes, it had lost its theological associations and become a loose formula, merely retained as a sanction for politics and morals, and a defence against the charge of atheism.