The Enlightenment promoted a more secular outlook in society by encouraging people to question received authority.
In Medieval times, people tended to accept ideas that came from authority figures. These could be figures from the past, like Aristotle, whose ideas were widely believed and taken on faith. These could also be people like church figures. The Enlightenment encouraged people to believe only in things that could be proven. This led to a more secular outlook in society as people stopped looking to the church for answers and instead turned to science for answers that could be backed up by empirical proof.