The Enlightenment period was from about 1637 - 1700 to about 1789 - 1804, scholars give various datings. Jane Austen was born toward the end of The Enlightenment, in 1775. She first wrote Pride and Prejudice, under the title First Impressions, in 1796 and 1797, though it was first published in 1813, which is a date scholars place after the close of the Enlightenment period. Jane Austen grew up while The Enlightenment was in full bloom and came to maturity in its waning years.
The Enlightenment was not a school of thought or movement. In fact, Enlightenment philosophies were often opposed to each other. The Enlightenment represented values that began with what Kant called a freedom to think for oneself and included the freedom to question institutions, morals, religions, and customs. A defining characteristic was a reliance on reason, empirical knowledge based on senses, and scientific rigor.
The affect of the Enlightenment period on Jane Austen's writing of Pride and Prejudice is seen in several points. First, the affect is seen in Austen's opposition to the sensibility of romanticism as when Mr. Bennet expresses the folly of marrying for beauty. Second, it is seen in Austen's advocacy of rational reasoning minds as seen in Mrs. Gardiner and Charlotte Lucas. Third, it is seen in Austen's questioning of traditional attitudes and beliefs as in Elizabeth's attitude toward Lady De Bourgh and in Charlotte's views opposing marrying for love. Fourth, it is seen in dependence on thinking for oneself as Elizabeth and Darcy learn to do.