Although the period known as the Enlightenment took place a century before The Portrait of a Lady was written, the Enlightenment is the historical period that most influences the novel's characters and its story. Isabel, especially, is a product of Enlightenment ideas.

The Enlightenment was a philosophical, political, and literary movement that swept Europe and the United States throughout the 1700s. Its major feature was the elevation of reason and scientific observation above the mysticism and superstition of the Middle Ages. All traditions and conventions, from the religious to the political and social, were reevaluated. No idea or authority was to be accepted blindly or merely because it had been accepted in the past; only those ideas that could be supported by reason or proven scientifically were considered valid.

The idea of the superiority of the intellect led to the idea that human beings were essentially...