To contemporaries who subscribed to the Enlightenment, the term "reason" was to be contrasted to superstition. Even though Christians, too, believed in reason, they also wanted to make room for the possibility of Gods intervention, particularly in miracles. Such exceptions seemed to Enlightenment adherents to conflict with reason, which they argued demanded evidence to substantiate claims. To this day scholars still dispute whether enlightened thinkers faith in reason was so encompassing that it acted as a belief not all that different from religiosity.
Source: mfr 83.310