In the period known to British historians as “the long eighteenth century,” that is, from the Glorious Revolution of 1688 to the Battle of Waterloo in 1815, the word “genius” came to assume its modern meaning. Before this time it had referred either to a nonhuman spirit which acted as an individual's guardian, providing advice or support in the form of superhuman wisdom or strength, or to a universal spirit of generation. During this period it came to be applied to a particular kind of inventive human being whose natural talent (ingenium) made possible the outstanding achievements previously believed to have been brought about by a (or the) genius. The external or universal spirit became an individual with outstanding natural powers.

The modern concept of genius is, therefore, one aspect of that overall change in which the balance between the gods' bounty and human achievement shifted decisively toward the latter. Just as political rule came to be justified not by divine right or historical precedent but rather in terms of (more or less) democratic consent, or as, later, May Day ceased to be a celebration of the earth's fertility and became an assertion of the power of labor, so genius became a wholly human phenomenon, independently productive and deriving its value from itself. The sentiment which gave rise to the democratic imperative of Rousseau's Contrat social was the same as that which informed Blake's statement, “I must create a system or be enslaved by another man's.”