In the course of the 1690s and early 1700s, Thomasius acquired the reputation of being a religious “enthusiast,” someone who set aside the formulaic creeds of the institutional churches in favor of an anti-intellectualist “faith of the heart” of the individual. His beliefs were in many ways similar to those of religious mystics and the many millenarian religious sects, which were excluded from the three established churches, Lutheran, Catholic, and Calvinist, within the Holy Roman Empire. This side of Thomasius's thought has so far received little attention in the secondary literature, especially as it has seemed difficult to reconcile with his reputation as an enlightened thinker. But there are important reasons for paying attention to Thomasius's religious beliefs, one of which is that his contemporaries often regarded him as a controversial figure because of his religious heterodoxy. Another is that the connections between Thomasius's “enthusiastic” religious beliefs and his “enlightened” philosophical program of reforming “scholasticism” are closer than they might at first appear to be. For, although faith and philosophy were conceptually distinct, Thomasius also believed that they were dependent on each other, in particular, because religious faith was easily corrupted by the overestimation of the powers of the human intellect in religious matters. Although he was never opposed to philosophy as such, Thomasius criticized his opponents for exaggerating the extent to which it could be of any use in matters of faith. This skepticism about the usefulness of philosophical reasoning and the powers of the human intellect in religion was a long-standing preoccupation in Lutheran thought, dating back at least to the reintroduction of metaphysics into Protestant theological curricula at the end of the sixteenth century, if not to Luther himself.

The present chapter examines this relationship between faith and philosophy, and its complex development in Thomasius's thought between the late 1680s and the early 1700s. This development can be roughly divided into three phases.